The purpose of this study was to investigate the prevalence of renal disorders in the Jinzu River basin in Toyama Prefecture, Japan where Itai-itai disease was endemic, based on the results of epidemiological studies performed in 1967 and 1968. Furthermore, was there a regional accumulation of the prevalence of abnormal urinary findings in that area? Early morning urine samples were collected from 13 183 subjects (6155 men, 7028 women) who then responded to questionnaires about lifestyle and health. The subject participation rate was 90%. Our findings showed that subjects living in the area of the Jinzu River basin have significantly higher prevalence of abnormal urinary findings compared to subjects living in neighboring river basins and these geographical distributions demonstrated a definite regional accumulation in those areas. The findings of this study verified the regional accumulation of renal disorders in the Jinzu River basin and indicate an association of the occurrence of renal disorders with the water from the Jinzu River.