Individuals differ in their hedonic response to sweet: sweet likers show increasing liking with increasing sucrose concentration, while sweet dislikers show increasing dislike with increasing concentration. Our results indicated that naive raters can correctly classify sweet likers and dislikers by observing subjects' facial responses to the taste of sucrose. Also, for both adults and children, the sweet liker/disliker distinction correlated strongly with the genetically determined ability to taste 6-n-propylthiouracil (PROP): PROP nontasters were almost always sweet likers, whereas sweet dislikers were almost always PROP tasters. Sweet dislikers also reported a purer sweet sensation than likers, who perceived nonsweet components in pure sucrose solutions. These results suggest that the sweet liker/disliker distinction is robust and valid, and that sensitivity to PROP may influence preference for sweet by altering the quality of sweet.