Forty-six unassertive Ss were randomly assigned to assertion training (AT) or waiting-list control conditions. Ss receiving AT showed significantly greater improvements from pretreatment to post-treatment on 8 out of 10 questionnaire measures of assertiveness and 3 out of 5 direct behavioral observation measures compared with the waiting-list group. 27 Ss who had completed the AT program were then randomly assigned to 1 of 3 booster conditions, namely, monthly assertion training boosters (ATB), monthly attention placebo boosters (APB), or no boosters (NB). At the 3-month follow-up there was minimal difference between booster conditions. By the 6-month follow-up the results favored the ATB condition. Although the APB procedure was effective in preventing the relapse shown by the NB subjects, the ATB group actually showed further improvements on some measures of assertiveness during the 6-month follow-up period.