The ultimate aim in the management of the persons with mental illness is to help them develope meaningful social relationships in their daily lives and th readapt themselves to their family and social life as an independent indivadual. These goals might be attained by modifying their behaviour patterns and/or inappropriate way of thinking. Recently, social skill training such as assertive behaviour has become regarded as a significant therapeutic method. This study was to provide baseline date in orders to develope nurse skill in an assertive training program as a prospective psychiatric nurse specialist. The subjects were persons with mental illness who were admitted in psychiatric inpatient unit or day care center of J Clinic in K City and date were collected from June 15 to September 17, 1993. The study was one group pretest-posttest experimental design. As a study too, assertive training program developed by Rakos & Schroeder and another assertive training program developed by Alberti & his colleagues were reformed and packaged for this stydy. The level of anxiety was tested by spielberger`s scales on trait and state anxiety. The level of assertiveness was tested by Rathus` assertive behaviour scale and that of sociality was tested by sociality was tested by social situation questionaire developed by Trower, Bryand and Argyle. The data were analyzed by Wilcoxon matched - pair signed - ranks test. The results of this study were summarized as follows : 1. The scores of state anxiety in posttest were significantly decreased(T=2.5, P<.01), but there were no significant differences in the scores of trait anxiety between pre and posttest(T=12.5, n.s.) 2. The scores of assertiveness in posttest were significantly increased(T=-5.5, P<.025). 3. There were no significant difference in the scores of sociality scores between in the scores of sociality scores between pre and posttest(T=12.0, n.s.).