Crescentic lupus glomerulonephritis (greater than or equal to 50% crescents) occurred in 16% of systemic lupus erythematosus (SLE) patients biopsied over a 32-month period. All had underlying WHO class IV lupus nephritis. These patients more frequently manifested with acute renal failure usually of the non-oliguric type, had heavier proteinuria and lower serum albumin, but were otherwise indistinguishable from non-crescentic WHO class IV lupus nephritis in their other renal and extrarenal manifestations or in their serological findings. Crescentic lupus glomerulonephritis may occur in patients at first presentation with SLE, or develop in patients after prolonged follow-up initially for lupus nephritis of WHO class IV or other classes. Combined methylprednisolone pulse therapy, immunosuppressives, antiplatelet agents with or without anticoagulant produced good initial responses. Prognosis was unfavorable for inadequately treated patients or for patients with persistent nephrotic syndrome and crescents.