Acquired cystic disease of the kidney in chronic glomerulonephritic patients who had been on hemodialysis more than 3 years (4.5 +/- 1.2 years at the base line examination), were followed for 3.6 +/- 0.5 years (at the follow-up examination) by computed tomography (CT scan). The renal volume in the 25 male patients was significantly greater at the follow-up examination than at the base line examination. On the other hand, the renal volume in the 12 female patients was similar on both examinations. The enlargement of kidney volume more than twofold during the follow-up was seen in 9 of 25 male and none of 12 female patients. The grade of cystic transformation was increased in male patients during the follow-up period. These results indicate that sex-related endogenous substances might play a role in the pathogenesis of acquired cystic disease.