Of 403 patients with renal and ureteric calculi treated during the last 4 years, 64 presented with features of chronic renal insufficiency: 59 of these underwent surgery. Good pre-operative preparation and conservative renal surgery restored normal renal function in 14 patients and 27 improved significantly. The remainder either did not improve or continued to have progressive renal failure. It is emphasised that these patients are considerably worse off compared with their counterparts with normal renal function. The overall mortality rate was 17%. Patients whose post-operative serum creatinine levels did not stabilise to less than 884 mumol/l seemed to make poor progress in the follow-up period.