A study was undertaken over a period of one year to assess the place of percutaneous renal biopsy in clinical nephrology. During this time 83 patients were biopsied. In 76 patients (92 percent) renal tissue was obtained at the first attempt. In the other seven patients renal tissue was obtained on a repeat biopsy after ultrasonic localisation of the kidney. Adequate renal tissue for a full histological interpretation was obtained from 82 of the 83 patients. The commonest indications for biopsy were a suspected systemic disorder, persistent proteinuria with or without the nephrotic syndrome, and abnormal renal function. In 18 patients the provisional clinical diagnosis was shown to be incorrect, while in another 17 the diagnosis was made solely on histological grounds. In only seven patients was there no histological diagnosis made. A wide spectrum of renal lesions was seen and in 35 patients the renal biopsy findings had a significant influence on patient management. Five patients developed macroscopic haematuria and one a perirenal haematoma. Percutaneous renal biopsy performed by an experienced physician and having the support of an expert histopathology service is a safe and valuable diagnostic aid for patients with a wide spectrum of renal and systemic disorders.