Although renal manifestations of the antiphospholipid syndrome (APS) have received scarce attention until recently, the kidney probably is a major target organ in APS. Thrombosis may develop at any location within renal vessels, ie, renal artery trunk or branches, intrarenal arteries or arterioles, glomerular capillaries, and renal vein. The clinical consequences consist of highly variable degrees of proteinuria; systemic hypertension ranging from mild to malignant; cortical necrosis; thrombotic microangiopathy, pregnancy-associated or not; and slowly to rapidly progressive renal failure that may require dialysis. These events occur mainly in the course of systemic lupus erythematosus or of "primary" APS. Renal involvement is a frequent feature of the catastrophic APS. A high prevalence of antiphospholipid antibodies has been reported recently in patients with end-stage renal failure, but their clinical significance remains to be determined.