To examine the effect of moderate and fatiguing exercise on the simple reaction times of recreational athletes, 12 subjects took a simple reaction-time test while at rest and while cycling on a Monark cycle ergometer at 70% and 100% of maximum workload. To estimate 70% and 100% of maximum workload the subjects underwent a standard incremental test until exhaustion, defined as subjects being unable to maintain the required pedal rate of 70 rpm. Simple reaction time during maximal exercise was significantly slower than in the other two conditions which did not differ significantly from one another. Heart rate and rate of perceived exertion differed significantly for all three conditions.