The highest hand and the lowest hand split the pot. In many high/low games, it is possible to win the entire pot by having the highest and the lowest hand (accomplished via wild cards, or by using different sets of 5 cards), but only if you declare that you're trying for both. If you try for both but don't win both (that is, someone else has the highest or the lowest hand), you win neither. When playing high/low, hands are compared against all other hands, not just the hands which are going the same way. Thus, if someone going high has a better low hand than all of the people going low, nobody going low wins (so the high hand gets the whole pot). If someone goes for both and fails, say by winning high but losing low, the high half of the pot goes to the low winner-- it doesn't go the second best high hand.