To assess the relative risk of treating all patients with the nephrotic syndrome with prednisolone as against making a complete diagnosis by all necessary means including renal biopsy, a retrospective study of patients with nephrotic syndrome was undertaken. It was shown that the risk of indiscriminate steroid therapy was more than 12 times greater than that of selective biopsy. It is recommended that the diagnosis of the cause of the nephrotic syndrome must always be established before embarking on therapy.