The purpose of this investigation was to examine the effects of preceding oral creatine monohydrate with a lacto-ovo-vegetarian diet on muscle creatine concentration. Thirty-two healthy men, who regularly consumed an omnivorous diet, were randomly assigned to consume a weight maintaining, lacto-ovo-vegetarian (LOV; n = 16) or omnivorous (Omni; n = 16) diet for 26 days. In addition to their assigned diet, on day 22 of the study, subjects were assigned in a double-blind manner to receive either creatine monohydrate (CM; 0.3 g · kg · d⁻¹ + 20 g Polycose) or an equivalent dose of placebo (PL) for 5 days. There were no significant differences between the LOV and Omni groups at baseline with respect to age, height, and weight. The results demonstrated that consuming a LOV diet for 21 days was an effective procedure to decrease muscle creatine concentration (p < .01) in individuals who normally consume meat and fish in their diet. However, muscle total creatine (TCr) following creatine supplementation did not differ statistically between LOV and Omni diet groups (148.6 ± 4.5 vs. 141.7 ± 4.5 mmol · kg⁻¹ d.m.).