The authors measured knowledge about medication and its side effects, impact of side effects, and compliance in 30 chronic outpatients before and after they participated in two instruction sessions about their medication held one month apart. Instruction consisted of a verbal or a written and verbal presentation and minimum or maximum information about side effects. All patients' medication knowledge increased after both sessions. Those on high doses of neuroleptics given verbal and written information gained significantly more medication knowledge than those given only verbal information. After instruction, more patients knew about specific side effects, including tardive dyskinesia, and both patients given only verbal instruction and those given minimum information about side effects had fewer problems with side effects. Instruction did not affect compliance.