The case records of 64 patients with 65 episodes of infectious gonarthritis during 1979-88 were reviewed regarding epidemiological, clinical and laboratory data of possible relevance to the course and outcome of the disease. Long-term healing results were evaluated by means of a new scoring system 2-11 years after the acute disease in 46 patients. The infection was acquired by inoculation in 37% and by the hematogenous route in 55%. The major risk factors were trauma to the joint and arthrosis. Staphylococcus aureus was the causative agent in 58% and Streptococci in 15%. Treatment consisted of suction irrigation (86%) or intermittent aspiration (5%) combined with systemic antibiotic treatment. At follow-up, the pain and ache scores of the arthritic joint had decreased by 21% and 16% respectively, compared with the scores of the contralateral control joints. Anatomy and motility were reduced by 9% and 8% respectively. Age < 45 was associated with a greater score loss than in older patients. Treatment delayed by > 5 days was associated with increased loss of motility. We estimate that 79% of the patients had excellent or good long-term results following treatment of infectious arthritis of the knee. Evaluation of healing after infectious gonarthritis by use of a scoring system is quite feasible and allows comparison of different treatment regimes with improved accuracy.