One rat was exposed to sequences of pre-determined numbers of shocks under the all-day-long experimental procedure which contained six 30-min sessions daily. In Experiment 1, three 1.5 sec shocks per session were imposed on a variable-interval 30-sec reinforcement schedule of lever pressing. The rat did not show any evident suppression of lever pressings. In Experiment 2, the procedure was modified so that the lever pressing was not reinforced before the third shock ended. The rat showed lever pressing suppression before the third shock, though some responses were often observed immediately after the second shock. This response pattern was influenced either by the change in the shock duration or the temporal position of shock delivery (the range of shock distribution). Finally the number of shocks was increased from three to five. The subject soon learned to suppress response until the fifth shock was delivered. These results were interpreted as showing that though the rat used some parameters of stimuli as cues for response suppression, the number of shocks was the effective element.