Streptococcus intermedius, included in the 'milleri group', is a commensal of the mouth and upper respiratory tract but it has often been associated with various pyogenic infections, such as endocarditis, pneumonia, abdominal or cerebral abscess, rarely with osteomyelitis, and exceptionally with muscular abscess. The first observed case of iliac osteomyelitis with gluteal muscle abscess caused by S. intermedius is reported. It is essential to recognise members of the 'milleri group' as possible agents of bone and muscle pyogenic infection because its management requires a timely diagnosis and prolonged antimicrobial treatment to achieve complete clinical and radiological recovery.