OBJECTIVE: To evaluate the performance of arbitrarily primed polymerase chain reaction (AP-PCR) analysis in epidemiologic typing of Legionella pneumophila. METHODS: Sixty-two isolates of L. pneumophila of serogroups 1, 3, 6 and 10, including epidemiologically related and unrelated isolates, were analyzed by AP-PCR using the primer BG2. Twenty-six of the serogroup 1 isolates were typed by pulsed-field gel electrophoresis (PFGE). RESULTS: AP-PCR analysis showed 98% typeability and complete reproducibility. A majority of unrelated isolates of each serogroup could be distinguished (discrimination index: 92%). Clinical isolates showed AP-PCR patterns indistinguishable from those of the isolates of the related environmental source. PFGE and AP-PCR results were in agreement for 88% of isolates. CONCLUSIONS: Single-primer AP-PCR analysis can be used as a simple and reproducible screening method for typing L. pneumophila strains of different serogroups.