Nine infants less than 2 months of age with group B streptococcal (GBS) osteomyelitis or septic arthritis, or both, were seen from January 1975 through January 1978. The infants had local joint signs, usually in the absence of systemic signs. The bones and joints involved were equally distributed between proximal humerus and proximal and distal femur. An infant had involvement of the talus. Treatment consisted of two to three weeks of parenteral antibiotics, arthrotomy in infants with arthritis, and bone decompression in infants with osteomyelitis. Clinical follow-up showed normal growth and function of the affected joint. Of the organisms, five were typed: four were type III and one was type Ib. Group B streptococcal osteomyelitis and/or septic arthritis was the second most common late-onset GSB infection, being surpassed only by meningitis.