The effect of creatine supplementation on exercise performance in vegetarians was examined. Creatine was ingested for 1 week by a group of vegetarians (VC) and meat-eaters (MC); a control group of meat-eaters was fed only glucose (MG). Exercise performance during three, 20-s maximal cycling tests (modified Wingate anaerobic test, WAnT) was determined before and after creatine supplementation. Blood samples were also drawn before and after exercise prior to and after supplementation. Basal plasma creatine (after an overnight fast) averaged (SE) 11 (2) microM in VC, and 24 (2) and 23 (7) microM in MG and MC, respectively (P < 0.05 for VC vs meat-eaters). These findings were expected, since most of the body's exogenous creatine source is meat. There was no significant difference in any other parameter between groups prior to supplementation. Creatine feedings significantly increased body mass (approximately 1 kg) and mean power output during the WAnTs (approximately 5%) to a similar extent in the VC and MC groups (P < 0.05-0.001). These parameters were not affected by supplementation in the MG group. Peak power output was also significantly increased by supplementation in MC (approximately 5%, P < 0.05), but not in VC. It is concluded that vegetarians and meat-eaters respond to creatine feedings with similar increases in mean power output during short-term, maximal exercise.