We report several cases in which patients with autistic disorder with mental retardation who received risperidone experienced urinary incontinence. We retrospectively investigated the medical records of patients housed in facilities for patients with autistic disorder with mental retardation. Those who had undergone a medical examination at a hospital in Tokyo from April 1999 to March 2009 were included in the study.Retrospective data were gathered including age, sex, IQ, birth weight, dosage of risperidone, urinary density, as well as existence of urinary and fecal incontinence. We divided the participants into those who did and did not experience urinary incontinence after taking risperidone and compared the 2 groups. Risperidone had been prescribed to 35 patients. In spite of the fact that no patient had a history of urinary incontinence, 14 patients experienced urinary incontinence after receiving risperidone. Moreover, 4 of these 14 patients also had fecal incontinence. Among the variables we examined, the only significant difference between groups was in sex, with significantly more women experiencing incontinence compared with men. When the dose of risperidone was reduced or the patients switched to other drugs, urinary incontinence of the patients improved.Hence, risperidone may have a casual relationship with urinary incontinence. Further research is needed to understand the pathophysiology of possible effect.