A method has been developed for the simultaneous analysis of vitamin A (retinol) and vitamin E (α-tocopherol) in stool. The method involves two extraction processes followed by normal phase HPLC with UV detection, 2,2,5,7,8 pentamethy-6-hydroxy chromanol having been identified as a suitable internal standard. The method has been applied to measure faecal losses of retinol and α-tocopherol in health and disease. The results support the view that the absorption of retinol in healthy individuals is virtually complete. However, the data suggests that the absorption of α-tocopherol may not be as efficient as has been reported previously. Subjects with cystic fibrosis experiencing steatorrhoea associated with pancreatic insufficiency were shown to be losing significantly greater amounts of retinol (P < 0.0001) and α-tocopherol (P < 0.001) in stool per day. There was a significantly higher concentration of retinol (P < 0.0001) and α-tocopherol (P < 0.05) in the stool of patients with cystic fibrosis compared to the controls i.e. 0.33 v 0 μg/g and 0.21 v 0.08 mg/g. In the cystic fibrosis patients 95% of the variation in the losses of retinol could be explained due to differnces in stool weight and faecal fat. Losses of α-tocopherol did not appear to be related to either stool weight, faecal fat or intake of α-tocopherol. subjects with chronic and acute infection showed no indication of retinol in the stool. Losses of α-tocopherol were however significantly lower, 0.05mg/g (P < 0.05) than those seen in the control group and those children with cystic fibrosis. Patients with cystic fibrosis lose variable amounts of these two fat soluble vitamins in stool and therefore the results highlight the need to measure losses in individual patients. The data would suggest that losses in the case of cystic fibrosis children are more likely to be a result of gastrointestinal abnormalities than due to respiratory infection.