Substance abuse is a major problem encountered by social workers in all settings. This study investigated the impact of a postmaster's program in the treatment of substance-abusing clients on the domains of "Attitudes and Values," "Knowledge and Skills," and "Behaviors" of its graduates. Overall, 91 percent of respondents found the program to be professionally beneficial to them. Significant increases were shown on all items in the "Knowledge and Skills Scale" and the "Behavior Scale". Among the greatest changes reflected in the "Attitudes and Values Scale" were increases in respondents' desire to add substance-abusing clients to their caseloads, their belief for good recovery prognosis, and their comfort level in being considered a substance abuse specialist. The results of this study indicate that completion of a comprehensive, long-term substance abuse training program not only increases clinicians' knowledge about substance abuse issues, but also impacts positively on their attitudes and behavior toward substance-abusing clients. (Contains 2 tables and 3 figures.)