An avoidance response was conditioned to three stimuli presented in serial order. Following conditioning, each group of subjects received a different treatment procedure. The group I procedure involved distributed CS trials, contingent, non-anxious CS terminations, and individualized treatment durations. Group 2 subjects received massed CS trials, non-contingent CS terminations, and non-individualized treatment durations. Group 3 subjects experienced distributed CS trials, contingent non-anxious CS terminations, and non-individualized treatment durations. Individual izing treatment duration (termination contingent upon operational ized measure of anxiety dissipation) was found to significantly hasten the extinction of avoidance responses. Implications for the effective practice of implosive therapy were discussed. Yoked control methods were criticized for confounding the variable of individualization of the yoked variable.