The effects of 0, 20, and 40min of free time in an exercise pen on pacing in circus tigers were investigated using three tigers traveling with two separate circuses (six tigers total). Each cat was subjected to each treatment at daily intervals following a Latin Square design and, except for practice or performances, held for the remainder of the time in their homecages. The tigers spent an average of 4.9±1.1% of their time pacing in their homecages, and this was not influenced by treatments (P=0.18). The cats traveled an average of 124.6m while in the exercise pen for 20min and 219.5m during 40min of access. There was a negative correlation between the distance traveled in the exercise pen for the 20- and 40-min treatments and the amount of time spent pacing in the homecage (r=−0.79 and −0.63). Performances and rehearsals appear to be important sources of additional exercise and stimulation that could account for why 20 or 40min of free time in an exercise pen did not influence pacing in the homecage. However, several tigers were active up until the end of the activity period, indicating that exercise pens are an important form of enrichment and that access for periods longer than 40min should be considered.