Sixty-four Ss practiced the rotary pursuit task in three different periods separated by rests, with the additional variable of massed (M) vs. distributed (D) practice, giving a total of eight groups. Massed practice was continuous, and distribution was made up of alternate intervals of 30-sec. work and 30-sec. rest. It was found possible to plot the development of conditioned inhibition during massed conditions and its extinction during subsequent distributed conditions. Temporary inhibition built up rapidly to a maximal level even under distributed conditions, and approximately 50% of this amount dissipated within a 30-sec. rest. Post-rest warm-up was found to begin immediately.