Well-trained, competitive swimmers were divided into two groups. Group A was given 900 IU alpha-tocopherol acetate daily for 6 months while group B was given placebos. A swimming endurance test was given before the start of supplementation and after 1, 2, 5 and 6 months. No difference in swimmers' endurance was observed between the two groups during the 6-month period. There was also no difference in postexercise serum lactic acid levels. Younger, less well-trained, competitive swimmers were also divided into two groups. Group A received 900 IU alpha-tocopherol acetate daily while group B received placebos. Swimming times for these swimmers were erratic, reflecting a lack of training. alpha-Tocopherol did not appear to have any effect on their swimming endurance.