Nocturnal enuresis has been recognized as an adverse effect of clozapine treatment. We reported 3 chronic schizophrenic patients who had showed nocturnal enuresis following clozapine treatment. Oxybutynin hydrochloride on clozapine-induced enuresis was very effective in 3 patients. The dose in our patients was 5 to 10mg/day. This medication was well tolerated. It is suggested that oxybutynin hydrochloride is a effective therapeutic option in clozapine-induced nocturnal enuresis.