Although infectious diseases are frequent in systemic lupus erythematosus, salmonella osteomyelitis is rarely reported. We here report an unusual case of salmonella osteomyelitis with osteonecrosis in a patient with systemic lupus erythematosus. A 29-year old woman with systemic lupus erythematosus was admitted to our hospital because of a painful swelling of right knee joint. She had been taking steroid and cyclophosphamide for 4 months because of diffuse membranous proliferative lupus nephritis. MRI showed both osteonecrosis of the right distal femur and osteomyelitis of the right proximal tibia. The abscess culture demonstrated salmonella species (non typhoidal). The infection was treated successfully by a combination of surgical drainage and intravenous ceftriaxone.(Korean J Med 58:112-116, 2000)