The incidence, clinical spectrum, types of streptococci in Thai adults with streptococcal arthritis in Chulalongkorn Hospital are similar to Western reports. The most frequently found organism was group A Streptococcus and the second was group G. Most of the patients were elderly who usually had underlying medical and/or joint diseases. There were 3 patients with underlying lepromatous leprosy which has never been reported before, while mixed types of streptococcal infection in the same joint, mixed types of streptococcal infection in the same patient and a patient with group C lumbar spondylodiskitis were also found. The most reliable diagnostic test is synovial fluid culture. All streptococcal isolates in our review were sensitive to penicillin and the clinical responses correlated with antibiotic sensitivity tests. Intravenous antibiotics and adequate drainage are the treatment of choice. The duration of treatment ranged from 4 to 6 weeks and most patients responded well. The overall mortality rate depended on host factors, organism virulence and treatment administered.