Detailed micturitional histories and urodynamic studies were conducted to investigate the micturitional disturbance in multiple system atrophy (MSA). Eighty-six patients with MSA comprised of 14 with striatonigral degeneration (SND), 42 with olivopontocerebellar atrophy (OPCA) and 30 with Shy-Drager syndrome (SDS). The results were as follows. Micturitional symptoms were noted in over 90% of patients with each type of MSA. Dominant symptoms were irritative ones in SND and OPCA, and a combination of irritative and obstructive ones in SDS. Micturitional symptoms in SDS appeared earlier than those in SND or OPCA. The degree of micturitional disturbance was severer in SDS than in SND or OPCA. Micturitional disturbance tended to become worse as the disease progressed. The responsible sites of lesions of micturitional disturbance seemed to be supra- as well as infranuclear lesions of the pelvic and pudendal nerves in MSA. Infranuclear lesions were more prominent in SDS than in SND or OPCA. Follow-up studies of some of the patients with SDS and OPCA suggested that the responsible sites of pelvic nerve lesions changed from supra- to infranuclear lesions during the course of disease.