Kaplan-Sheinwold (K-S) is a natural American bidding system that combines a weak 1NT opening of 12-14 points with five-card majors. Because the weak balanced hands open 1NT, a one-of-a-minor opening is either unbalanced or a strong balanced hand of 15 or more, and the notrump rebids are strong instead of weak.
Edgar Kaplan and Alfred Sheinwold built the system in the 1950s, and it used several ideas long before 2/1 Game Force players took them for granted: a forcing 1NT response, inverted minor raises, and two-level responses that commit to game. If you searched for "weak notrump five card majors", K-S is the classic answer. This guide covers its openings, responses and rebids, how it compares with 2/1, and who should try it.
What Is the Kaplan-Sheinwold System?
K-S was the partnership system of two of the best-known figures in American bridge. Edgar Kaplan was a champion player, an authority on the laws of the game, and for three decades the editor of The Bridge World magazine. Alfred Sheinwold wrote a syndicated bridge column for many years and the best-selling beginner book Five Weeks to Winning Bridge.
They described the system in How to Play Winning Bridge (1958), revised as The Kaplan-Sheinwold System of Winning Bridge (1963), and Kaplan kept refining it in The Bridge World for decades. At a time when almost every American pair played a strong notrump and four-card majors, K-S stood out by doing the opposite on the notrump and going further on the majors.
There is also a variant called Timid K-S, used by Kaplan with Norman Kay: the same system, but with a strong 1NT when vulnerable. It keeps the weak notrump for when you are not vulnerable, where a penalty double costs less.
Kaplan-Sheinwold Opening Bids
| Opening | Meaning in classic K-S |
|---|---|
| 1NT | 12-14, balanced: the weak notrump |
| 1♣, 1♦ | Unbalanced, or balanced with 15 or more |
| 1♥, 1♠ | Five or more cards |
| 2♣ | Strong and artificial: the only forcing opening |
| 2♦, 2♥, 2♠ | Weak twos |
The structure has a simple logic. Balanced hands come in three ranges: 12-14 opens 1NT, 15-17 opens a minor and rebids 1NT, and 18-20 opens a minor and rebids 2NT. Every one-of-a-minor opening is therefore either a real suit or a strong balanced hand, and responder can plan with more confidence than in a system where 1♣ may be a 12-point 4-4-3-2.
You are the dealer, playing Kaplan-Sheinwold. What do you open?
You are the dealer, playing Kaplan-Sheinwold. What do you open with this 13-point hand?
Your hand:
Why a Weak Notrump With Five-Card Majors?
Frequency. We counted every possible hand: a balanced 12-14 (4-3-3-3, 4-4-3-2 or 5-3-3-2) comes up about 9.7% of the time, a balanced 15-17 about 4.9%. So a weak 1NT opening appears about twice as often as a strong one. Each time, the next player must enter at the two level without knowing whether his side has a fit.
Cleaner minor openings. In 2/1 and SAYC, the weak balanced hands with no five-card major open 1♣ or 1♦, which makes those openings vague. In K-S they open 1NT, so a minor opening is either a real suit or a strong hand.
Five-card majors. K-S kept the main gain of five-card majors: responder can raise with three-card support at once.
The cost is the penalty double. 1NT doubled with 18-21 points between the two hands can be expensive, especially vulnerable. Every weak-notrump pair needs a runout agreement, and Timid K-S is one answer: play the strong notrump when vulnerable.
For the general debate, see weak notrump vs strong notrump and five-card majors vs four-card majors.
A weak notrump doubled and two down costs 300 not vulnerable and 500 vulnerable. Agree a runout before you play K-S, and decide whether you switch to a strong notrump when vulnerable.
Responses in K-S
K-S responses look a lot like modern 2/1:
| Response | Meaning in K-S |
|---|---|
| 1NT over 1♥ or 1♠ | Forcing for one round |
| Two of a minor over a major | Game forcing unless responder rebids his own suit |
| 1♠ - 2♥ | Can be lighter: about 10 points and five hearts |
| Single raise of a minor | Strong: inverted minors |
| Jump raise of a minor | Weak, preemptive |
| Jump raise of a major | Limit raise, invitational |
| Double of an overcall | Negative |
The two-level game force with one escape is the ancestor of modern 2/1. In K-S, 1♠ - 2♣ followed by a rebid of clubs is not forcing, so responder can bid a long minor with about 10-12 points. Pure 2/1 removes that escape: the hand goes through the forcing 1NT instead.
Inverted minors are a K-S trademark: 1♦ - 2♦ is the strong raise, about 10 or more with no four-card major, and 1♦ - 3♦ is weak. In the original K-S, both raises also promised five-card support. Many 2/1 pairs play inverted minors today.
Over a minor opening, K-S responder with a weak or moderate hand shows a four-card major before a longer minor, and bids the longer suit first only with game values. That is the same idea as Walsh style.
Partner opens 1♠. You play Kaplan-Sheinwold. Your call?
Partner opens 1♠ and you play Kaplan-Sheinwold, where a two-level minor response forces to game unless you rebid your suit. What do you bid with this 11-point hand?
Your hand:
Opener's Rebids in K-S
This is where K-S feels most different from 2/1:
| Auction | K-S meaning | 2/1 meaning |
|---|---|---|
| 1♦ - 1♠ - 1NT | 15-17, balanced | 12-14, balanced |
| 1♦ - 1♠ - 2NT | 18-20, balanced | 18-19, balanced |
| 1♦ - 1♠ - 2♦ | A minimum, often six diamonds | A minimum, six diamonds |
| 1♣ - 1♥ - 2♦ | A reverse, forcing | A reverse, forcing |
The 1NT rebid is the key. When a K-S opener rebids 1NT, responder adds his points to 15-17, not 12-14. With 10 points, responder bids game; with 8 or 9, he invites.
You opened 1♦ and partner responded 1♠. Playing K-S, what do you rebid?
You play Kaplan-Sheinwold. You open 1♦ and partner responds 1♠. What do you rebid with this 15-point hand?
Your hand:
Kaplan-Sheinwold vs 2/1 Game Force
| Topic | Kaplan-Sheinwold | 2/1 Game Force |
|---|---|---|
| 1NT opening | 12-14 (Timid K-S: 15-17 vulnerable) | 15-17 |
| Majors | Five-card | Five-card |
| 1♣ / 1♦ | Unbalanced or 15+ balanced | Three or more clubs; four or more diamonds unless 4-4-3-2 |
| 1NT rebid | 15-17 | 12-14 |
| 1NT response to a major | Forcing | Forcing (some pairs semi-forcing) |
| Two-level new suit | Game forcing unless responder rebids it | Game forcing |
| Minor raises | Inverted | Often inverted |
| Strong opening | 2♣ | 2♣ |
The two systems agree on more than they disagree. The real split is the notrump: K-S trades the safety of a strong 1NT for frequency and pressure, and moves the 15-17 hands into the rebid. A 2/1 player can learn K-S in an evening, but will forget the rebid ranges for weeks. Write them on the convention card in big numbers.
Who Plays K-S Today?
Pure K-S is rare now, but its ideas are everywhere. The forcing notrump, inverted minors and the two-level game force live on in 2/1, and Bridge World Standard, the expert consensus system published by the magazine Kaplan edited, carries many of them (see Bridge World Standard). Pairs who want the K-S notrump with a modern structure can play a weak notrump inside an otherwise 2/1 framework.
To see how a weak notrump changes the meaning of the same call, compare what 1NT means in every system on the free bid meaning page: Acol uses a 12-14 notrump like K-S, while 2/1 and SAYC use 15-17. Then practice weak-notrump auctions by setting the robots to Acol in the Bidding Room.