The etiology of crescentic nephritis (CN) in the developing world differs from that of Europe and North America. This retrospective study of 73 patients is the largest series of CN in the developing world. The records of all renal biopsies performed at Groote Schuur Hospital, Cape Town, South Africa, over thirteen years, between January 1977 and April 1991, were reviewed. Specimens selected for this study had six or more glomeruli and over 50% of these glomeruli had crescent formation. It confirms that post infectious glomerulonephritis (PIGN) (n = 21) is the commonest cause of CN in this setting. In addition there were 15 patients with CN associated with systemic lupus erythematosus (SLE). These two groups make this study unique as they are the largest series of each described in the literature. Thirty-nine (53%) patients in this series progressed to end-stage renal failure (ESRF) and only nine (12%) patients recovered renal function to a normal serum creatinine. Eight (38%) patients in the PIGN group developed ESRF, indicating the poor prognosis of this condition. Six of eight patients in the PIGN group treated with steroids and cyclophosphamide recovered to a serum creatinine level less than 200 mumol/l and only one progressed to ESRF, which may indicate that this form of therapy is beneficial. Thirteen (87%) patients with SLE either developed ESRF or died which suggests that the presence of crescents in this condition is associated with a poor prognosis.