Fusobacterium species are anaerobic Gram-negative bacilli, which cotonise the mucus membranes of man and animals and can cause a number of clinical manifestations including Lemierre ' s disease (postanginal septicaemia), abdominal infection and deep-seated abscesses. The incidence of fusobacterium infections appears to be increasing, and we present three cases of fusobacteriosis who presented with features of community acquired pneumonia (CAP). Cases were treated with benzyl penicillin and metronidazole, co-amoxiclav and metroniclazole and amoxicillin and clarithromycin. Since some of the Fusobacterium species are resistant to penicillin and erythromycin, treatment with these antibiotics in cases of fusobacteriosis presenting as CAP may lead to treatment failure. A high index of clinical suspicion is required to recognise this rare cause of CAP. (c) 2003 The British Infection Society. Published by Elsevier Ltd. All rights reserved.