Summary Purulent pericarditis is an infrequent, but important complication of infective illnesses, in particular pneumonia, which if diagnosed early has a good prognosis. The incidence of the condition is probably increasing, particularly in the immuno-compromised group of patients. ‘Classical’ symptoms and signs are often absent, and a high index of awareness is required to diagnose the condition. This review deals with the epidemiology, microbiology, clinical features, treatment and prognosis of purulent pericarditis with two illustrative examples of typical cases.