The racial distribution of the findings in 664 renal biopsies was studied for the state of New Mexico. The incidence of IgA-related nephritides (Berger's disease and Henoch-Schönlein purpura) was significantly greater in American Indians than in Hispanics and Anglos; IgA-related nephritides were found in 38 per cent of renal biopsies in American Indians. The clinicopathologic presentations of IgA-related nephritides were similar in the three ethnic groups.