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An attempt was made to reduce a loud high-pitched respiratory stridor in a 52-year-old male hospitalized for paranoid schizophrenia. Four consecutive schedules of electric shock were employed over a period of 68 days. Each treatment session lasted 15 min per day and consisted of ninety 10-sec intervals. In Schedule I (10 days), the subject was shocked every 10 sec if he emitted four or more stridors. In Schedule II (28 days), the subject was shocked if he emitted three or more stridors during each 10-sec interval. In Schedule III (15 days) shock was delivered immediately after the emission of a stridor, and in schedule IV (15 days) the shock switch was depressed immediately after the subject emitted a stridor but no shock was delivered. While the first schedule yielded a reduction in the subject's stridor, a greater decrease was found during Schedule II, wherein almost complete elimination of the behavior occurred. Schedules III and IV both had deleterious effects, with the former schedule showing the greater increase in the stridor. The differential effects of these aversive schedules are discussed.