San Francisco convention

The San Francisco convention (also referred to as the Warren convention) is a bidding convention in contract bridge intended to be used to investigate the slam possibility of the combined hands of the partnership. It allows one partner to gain information on the number of aces and kings in the other partner's hand using one asking bid only.

With this convention, a bid of 4NT asks partner to give a count on aces and kings with aces counting as three points and kings as 1 point. The replies to the 4NT asking bid are:

:5Clubs : less than 3 points:5Diams : 3 points:5Hearts : 4 points:5Spades : 5 points:5NT : 6 points:etc.

Obviously, there is some ambiguity in these replies. For instance, a 5Hearts response can indicate an ace and a king or four kings. Central idea behind this convention is that asker, based on the response and his/her own hand, will always be able to infer the number of aces and number of kings partner is holding. In case of the 5Hearts response, for instance, the responder must have one ace and one king if the asker holds at least one king.

The convention is not aligned with the useful space principle and can bring the partnership to a too high level.

The convention has largely been superseded by ace finding conventions, in particular the Blackwood convention and its variants. For a similar method, see: Norman four notrump.

References

*Francis, Truscott and Francis, "The Official Encyclopedia of Bridge", 6th edition (2001), ISBN 0-943855-44-6