This is a 4 No Trump convention, which is sometimes referred to as the Warren convention. It is sometimes also referred to as California Blackwood. Many bridge historians have also recognized and classified the San Francisco convention as a variation of the Norman convention as originated and developed by Sir Norman Bennett and Mr. Norman V. Hart.

Background and Principle of the Concept

It was used by many bridge players when the game of bridge was evolving and it is, to some degree, very similar to the concept of the Culbertson Four-Five No Trump convention.

The origin of the designation of the convention is unknown, but it is rather evident that not only the state of California, United States, but also the city of San Francisco, California, United States, wished to be immortalized in the annals of bridge history via a conventional method. However, the developer or originator remains unknown.

The conventional method is employed once a trump suit has been established and one partner triggers a slam try.

The 4 No Trump opener is required to hold at least two Aces before being able to make this opening. The responses by the partner show the holding of both Aces and Kings by using only one bid. In order to accomplish this, the Aces are counted as 3 points and the Kings as 1 point, and the responses are shown below.


South   West   North   East   Meaning
1   Pass   3   Pass   North shows a game-forcing raise.
4 NT   Pass           South initiates the San Francisco Convention and asks for Aces.
        5       Shows 4 points: 1 Ace and 1 King, or 4 Kings.


5 : Shows fewer than 3 points or zero to 2 points: no Ace and at most 2 Kings.
5 : Shows 3 points: 1 Ace and no Kings, or 3 Kings.
5 : Shows 4 points: 1 Ace and 1 King, or 4 Kings.
5 : Shows 5 points: 1 Ace and 2 Kings.
5 NT: Shows 6 points: 1 Ace and 3 Kings, or 2 Aces.
6 : Shows 7 points: 2 Aces and 1 King, or 1 Ace and 4 Kings.
6 : Shows 8 points: 2 Aces and 2 Kings.
6 : Shows 9 points: 2 Aces and 3 Kings.
6 : Shows 10 points: 2 Aces and 4 Kings.

Variation by Mr. Arthur Mathisen

Note: A contribution by Mr. Arthur Mathisen, emailed on date May 7, 2011, offers a variation, in which the first response of 5 Clubs shows zero to and including 3 points. The bid of 5 Diamonds would then show 4 points, etc. We are grateful to Mr. Arthur Mathisen for the contribution of this variation.

Employment Following a Strong, Artificial Two-Bid

The responder can also show the number of points for the Aces and Kings even if the opener decides to open the auction with a strong, artificial 2 Clubs bid, and/or, by partnership agreement, a Strong Two-Bid in any suit. After this opening the responder uses other bids to communicate to partner the number of points held.

Note: The reader should remain cognizant of the fact that many bridge authors and more experienced players employed Strong Two Bids in all suits as opening bids to show strong hands, for which the parameters were described and defined by bridge experts during the 1940s to the 1970s.

Note: Among the pioneers and promoters of such bridge bidding tactics was Mr. Charles Goren with his original bidding system, which he promulgated and popularized in several publications. Such opening bids, however, were proven to have less employment frequency by other bridge experts such as Mr. David Burnstine (Bruce) of the United States and Mr. Pierre Albarran, born in the West Indies, but who resided in Paris, France.

The responses are outlined below, all of which were a jump to the five level to show the number of held values.

Opener Responder Meaning
2 /// 5 Shows no points.
5 Shows 1 point.
5 Shows 2 points.
5 Shows 3 points.
5 NT Shows 4 points.
6 Shows 5 points.
6 Shows 6 points.
6 Shows 7 points.
6 Shows 8 points.
6 NT Show 9 points, etc.

In the case of Strong Two-Bids, made in any suit, the immediate jump to the five level proves to be cumbersome upon the partnership since much of the bidding space has been eliminated. The possibility and the percentage of ambiguity is increased since the opener must decide as to the number and/or location of Aces and Kings held by inference.



If you wish to include this feature, or any other feature, of the game of bridge in your partnership agreement, then please make certain that the concept is understood by both partners. Be aware whether or not the feature is alertable or not and whether an announcement should or must be made. Check with the governing body and/or the bridge district and/or the bridge unit prior to the game to establish the guidelines applied. Please include the particular feature on your convention card in order that your opponents are also aware of this feature during the bidding process, since this information must be made known to them according to the Laws of Duplicate Contract Bridge. We do not always include the procedure regarding Alerts and/or Announcements, since these regulations are changed and revised during time by the governing body. It is our intention only to present the information as concisely and as accurately as possible.


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