Increased consumption of vegetables and fruit has long been the focus of dietary strategies for disease prevention. Some vegetables and fruit have bitter tastes, which can be aversive to consumers, particularly children. The present study tested the hypothesis that acceptance of grapefruit juice is influenced, in part, by sensitivity to the bitter taste of 6-n-propylthiouracil (Prop), a heritable trait. A sample of 123 women, mean age 28 y, was divided into nontasters (n = 39), tasters (n = 49), and supertasters (n = 35) of Prop by using procedures validated previously based on Prop detection thresholds and on intensity scaling of five suprathreshold solutions of Prop and sodium chloride. The subjects tasted and rated five solutions of the bioflavonoid naringin in 4% sucrose. Naringin, the principal bitter ingredient of grapefruit juice, has been implicated in the regulation of cytochrome P-450 enzymes. Increased taste acuity for both Prop and naringin was associated with greater dislike for each bitter compound. Prop supertasters disliked bitter naringin solutions significantly more than did either tasters or nontasters. Prop sensitivity was also associated with reduced acceptability of grapefruit juice. Acceptability of orange juice, which does not contain naringin, was unrelated to Prop taster status. Is the acceptability of other bitter vegetables and fruit also limited by inherited taste factors? If so, then genetic taste markers might limit dietary exposure to valuable dietary constituents and pose a barrier to current strategies for dietary change.