Sixteen cases of suppurative arthritis of the hip in fifteen infants who had had femoral venipunctures are reported. Twelve of the fifteen infants had neonatal jaundice. Although bacteriological evidence to prove the causal relationship between the venipuncture and hip-joint sepsis was not available, the circumstantial evidence was strongly suggestive. The findings in this study emphasized that the diagnosis of acute septic arthritis in the acutely ill infant is still frequently missed and that failure to make a prompt diagnosis results in irreparable damage to the hip. It was concluded that femoral venipuncture should be avoided so far as possible and that any infant who has had femoral venipuncture should be closely observed for evidence of septic arthritis of the hip and septicemia.