Under the given constraints, partner's possible distributions are: Short ♣, 1 case, 4-4-4-1 Short ♦, 1 case, 4-4-1-4 Short ♥, 3 cases, 4-1-4-4, 4-0-4-5, 4-0-5-4 Short ♠, 3 cases, 1-4-4-4, 0-4-4-5, 0-4-5-4 Given that partner will be short in a major suit 6/8 times and in a minor suit only 2/8 times, and our side will always have 4-5 cards when short in a minor suit, but only 3-4 cards when short in a major suit, I think a minor suit lead has a greater chance of being successful. I'll pick a club, only because we rate to hold more clubs (either 8 or 9) than any other suit, as long as clubs is not partners shortness. However, I'm sure this is wrong and I am leading into AKQ10xxxx. :) EDIT: I also think that RHO may well have only an 8 card suit headed by the AKJ10, rather than the 9 or 10 card suit that was suggested by others, if that makes a difference.