The lever pressing of five adult, female gerbils was maintained on fixed-interval schedules with interval values of 20, 60, and 180 sec. Performance was characterized by a pause after reinforcement followed by either an acceleration of responding or a constant response rate until the next reinforcer was obtained. Overall response rates and response rates calculated to exclude postreinforcement pauses (running rates) varied unsystematically with changes in the fixed-interval parameter, higher response rates tending to occur with shorter intervals. The average postreinforcement pause durations, however, were systematically related to the interval value, pause durations increasing with increases in the interval size. Gerbils thus show patterns of fixed-interval responding similar to those of other species and appear to be convenient subjects for use in studies of operant behavior.