Study aim: To find out whether a 6-week creatine supplementation would significantly augment body mass and muscle circumferences in male bodybuilders.Material and methods: A group of 14 male bodybuilders aged 16 - 29 years were randomly divided into two groups: experimental (E) and control (C), 7 subjects each. Group E received creatine monohydrate, Group C - placebo, 10 g daily for 6 weeks without saturation phase. The experimental design was a double-blind one. All subjects were on strictly controlled diet, the daily intakes amounting to 2.3 - 2.8 g of protein, 1.0 - 1.2 g of fat and 5 - 6 g/kg body mass of carbohydrate, and 3200 - 4000 kcal. All subjects trained 3 days a week, each session lasting 120 min, in the ‘Power, Rep-Range, Shock’ mode. Chest, waist, arm, forearm, thigh and calf girths were measured in the relaxed and contracted states, together with body mass, before and after the study.Results: Significant, training-induced changes were noted in almost all body circumferences studied in both groups and muscle states, those in the chest, biceps and thigh girths being the most pronounced ones and significantly (p<0.05) greater in the experimental than in control group in the contracted muscle state. In the relaxed state the between-group differences were significant for the chest and thigh girths. The increments in body mass were significantly (p<0.01) higher in the experimental than in control group (4.3 ± 1.3 and 2.1 ± 0.7 kg, respectively).Conclusions: The observed changes may have been brought about by creatine administration.