Cases of osteomyelitis can be divided into four categories: acute hematogenous, vertebral, secondary to a contiguous focus of infection without vascular disease, and secondary to a contiguous focus of infection with vascular disease. Each category may be further divided into acute and chronic forms. Clinical symptoms persisting for ⩾10 days correlate roughly with the development of necrotic bone and chronic osteomyelitis. Patients enrolled in clinical trials should generally be ⩾12 years of age. Prior antimicrobial treatment does not exclude patients if the culture of a bone sample obtained at the time of enrollment yields pathogenic bacteria. Randomized, double-blind, active-control comparative studies are encouraged. Clinical outcome should be assessed during therapy and within 5–9 days, 4–6 weeks, and 11–13 months after completion of therapy. In the final assessment, clinical appraisal is paramount.