1. Oral creatine supplementation has been shown to increase muscle creatine and phosphocreatine concentrations with consequent benefits on performance during short-term maximal exercise. However, recently there have been anecdotal reports that creatine supplementation can also influence the pattern of substrate utilization and improve performance during more prolonged, submaximal exercise, which, based on recent experimental evidence, may have some scientific justification. 2. Eight men performed a continuous incremental exercise test running at 10 km/h on a motorized treadmill at predetermined workloads from 50% to 90% of maximal oxygen uptake, before and after 5 days of creatine supplementation (4 x 5 g daily). Exercise was performed for 6 min at each workload to achieve a steady state, and respiratory gas exchange and blood lactate concentrations were measured during the last 30 s at each workload. Measurements were also made at 5-min intervals for the first 15 min of recovery. 3. The results showed no measurable effect of creatine supplementation on respiratory gas exchange and blood lactate concentrations during either incremental submaximal exercise or recovery. This suggests that creatine supplementation does not influence substrate utilization during and after this type of exercise.