In a patient with an exacerbation of systemic lupus erythematosus with neurological involvement, Serratia species septicemia developed. This responded to appropriate treatment. However, septic arthritis of the left hip with the same organism subsequently developed and required surgical débridement and removal of the left femoral head. The rarity of arthritis due to Serratia species is noted and the possible role of multiple femoral artery punctures contributing to the pathogenesis of this unusual complication of septicemia is discussed.