The ability of lactose-intolerant individuals to tolerate 8 ounces of milk was determined in healthy teen-agers. Thirty-two blacks were studied with 50-gm lactose tolerance tests. Nineteen (59%) had a flat blood sugar curve and 13 (39%) also developed bloating, cramps, loose stools, or diarrhea with the test. These latter 13 were defined as lactose-intolerant. Seven of the 13 lactose-intolerant teen-agers (54%) developed abdominal bloating and/or cramps after drinking 8 ounces of milk (half-pint). None had diarrhea. Eight were symptomatic with the equivalent amount of lactose (12 gm) while only one had symptoms with the monosaccharide components of lactose, glucose and galactose. The symptoms with milk and 12 gm of lactose were less severe than with the 50-gm tolerance test. A history of a prior awareness of milk intolerance was obtained from 11 of the 13 lactose-intolerant subjects. At least one half of lactose intolerant teen-agers might be expected to be symptomatic after drinking 8 ounces of milk without other food. Milk intolerance should be considered in the nutritional planning for teen-agers with special attention to members of population groups with a high prevalence of lactose intolerance.