Pyogenic vertebral osteomyelitis is a disease of adults that should be distinguished from true disk space infection. It is due to a hematogenous seeding (either venous or arterial) of the subchondral bony elements of the vertebral body. The disk space is involved secondarly, later in the course of the disease. The underlying bacteremia is from another focus of infection, frequently in the urinary tract. Disk space infection in adults is caused by direct violation of the disk, most commonly at the time of surgical excision of the nucleus pulposus. The bony elements of both adjacent vertebral bodies are secondarily involved. The clinical feature common to both types of infection is back pain that generally begins insidiously and then gradually increases in severity and becomes continuous and is accompanied by marked muscle spasm. The sedimentation rate is always increased; it decreases only with resolution of the infection. The diagnosis of vertebral infection is often not suspected because fever and leukocytosis generally are absent. The most common organism is Staphylococcus aureus, although gram-negative bacterial infections also occur. Bacteriologic diangosis should be sought in each case by blood cultures (generally negative with postoperative disk space infection) or percutaneous needle biopsy. Soft tissue abscesses may require open débridement and drainage. Treatment of both types consists of rest, immobilization, and specific antibiotic treatment. The prognosis for resolution of the infectious process within six to nine months, with adequate treatment, is excellent.