Hydrogen breath tests were performed on 10 healthy adults after they had ingested a mixture of sorbitol and fructose, in which these substances were present in amounts corresponding to the individual absorption capacities. A significant malabsorption of this mixture was evident in 7 of 10 subjects. The mixture caused mild to severe gastrointestinal distress in five subjects. When the carbohydrates were given separately, symptoms were absent. There was a significant correlation between the individual absorption capacities of fructose and of sorbitol. A mixture containing a similar amount of fructose, but given as sucrose, and a similar amount of sorbitol was further given to four of the seven subjects showing malabsorption of the fructose-sorbitol mixture. Malabsorption now failed to appear, and symptoms were absent. These findings are of potential importance for the understanding of the physiologic processes involved in fructose absorption and suggest that in healthy adults the presence of sorbitol interferes with fructose absorption and/or vice versa. An interaction between small amounts of fructose and sorbitol causing malabsorption and abdominal distress has not been demonstrated previously. Gastrointestinal discomfort must be suspected to occur in sensitive individuals at a rather limited daily intake of fructose- and sorbitol-containing foodstuffs.