Most patients with SLE develop kidney disease related to this systemic underlying disease process. Lupus nephritis is an important cause of morbidity and even mortality in patients with systemic lupus erythematosus. Lupus nephritis has diverse morphologic manifestations with varying clinical presentations and consequences. The pathogeneses involve immune complexes, which can deposit anywhere in the kidney, and other mechanisms, including endothelial injury, podocytopathy, and tubulointerstitial injury. Treatment and prognosis accordingly range from excellent even with only observation with minimal mesangial deposits, to kidney failure despite aggressive immunosuppression in patients with severe proliferative disease. Renal biopsy plays a crucial role in the diagnosis of the specific form of lupus nephritis in any patient. However, the role of the renal biopsy in prediction of outcome, treatment, and prognosis has been controversial. We will review the current classification of lupus nephritis and the value of renal biopsy in the management of these patients.