This study was conducted to investigate the effects of giving short-term doses of creatine by mouth to healthy older male subjects, taking into account their training status. A group of 42 volunteers was divided into three: a sedentary group composed of elderly sedentary men [n = 14, mean age 70.1 (SEM 1.2) years], a trained group composed of elderly trained cyclists [n = 14, mean age 66.4 (SEM 1.4) years] and a young group composed of young sedentary men [n = 14, mean age 26.0 (SEM 1.2) years]. In each group, double-blind randomization was carried out: one half was given creatine (3x5 g x day(-1)), and the other was given an iso-nitrogenated placebo (3x10 g x day(-1)). Before and after the 5 days during which the supplements were given, all subjects performed five all-out 10-s sprints separated by 60-s intervals of passive recovery, seated on a cycle ergometer. Power output, work done and heart rate data were recorded during each sprint. The elderly and the young sedentary subgroups given creatine showed significant (P < 0.05) improvements in maximal power (+3.7% and +2.0%, respectively) and work done (+4.1% and +5.1%, respectively) in the subsequent tests. In contrast, no significant change in pedalling performances was observed in the trained elderly subjects. The creatine did not change the exercise and recovery heart rate profiles, in any group. Our study suggested that creatine given by mouth increases the anaerobic power and work capacity of sedentary people of different ages during maximal pedalling tasks. However, the level of physical activity seems to be a determinant of the ergogenic effect of creatine in older subjects.