A 53-year-old woman was admitted because of a two weeks' history of progressive perineal pain, low-grade fever, a high erythrocyte sedimentation rate, and tenderness over the inferior rami of the pubic bone. Osteomyelitis was suspected. However, bone scanning, computed tomography, and magnetic resonance imaging of the pelvis showed no evidence of intraosseous disease, but revealed signs of inflammation in the surrounding soft tissue. Conventional antimicrobial therapy was unsuccessful. Biopsy of the bone demonstrated active osteomyelitis and the cultures grew Pseudomonas aeruginosa. Osteomyelitis of the pubic bone and symphysis is most often a sequel to pelvic surgery but has also been observed in i.v. drug abusers. In both circumstances Pseudomonas aeruginosa has frequently been identified as the causative agent. Pelvic osteomyelitis is extremely rare in patients without predisposing factors. Osteomyelitis can only be differentiated from osteitis pubis, a non-infectious inflammatory disease, by bone biopsy. The treatment of choice for osteomyelitis is a beta-lactam antibiotic effective against pseudomonas in combination with an aminoglycoside for 4-6 weeks. Recent studies have demonstrated that new generation quinolones are also effective.