Over a 12-month period, 150 patients were seen at an acute arthritis clinic to assess the type of case not usually seen in our chronic service, where delays of up to 24 weeks may occur before patients can be investigated. The majority of patients in whom the diagnosis could confidently be made had either gout or reactive arthritis, and, while the former diagnosis was unlikely to be missed, many practitioners seemed unaware of the type of presentation and variety of organisms that can cause reactive arthritis. Despite intensive investigation, a diagnosis could not be made in some cases. Those with septic arthritis had a better prognosis than patients in a previous series from this centre. Early referral leading to prompt diagnosis of this serious complication may have been an important factor in the improved outcome.