In a cross-sectional study adjusting for age, gender, and catchment area, the prevalence of thyroid antibodies was assessed in 51 consecutive subjects with biopsy-proven glomerulonephritis and in 112 control subjects admitted for extracorporeal shock-wave lithotripsy treatment for renal stones. Women with glomerulonephritis had both a significantly greater prevalence of thyroid peroxidase antibodies (odds ratio 3.85, 95% confidence interval 1.04-14.3) and an increased prevalence of elevated serum TSH values (P = 0.007). No such difference was found in men. The prevalence of thyroglobulin antibodies did not differ between the groups. It is suggested that the possibility of an autoimmune thyroid disease should be taken into consideration in patients with glomerulonephritis, particularly in women.