SUMMARYTwo isolations of Arizona from humans were made in Sheffield in 1966. The first was from a 3-year-old girl with a history of gastro-enteritis; the second was from her 5-year-old brother who was a symptomless excretor. Infection was traced to pet terrapins recently purchased from a local pet shop. The relative epidemiological significance of Arizona infection and the potential hazard of pet terrapins has been reviewed.We wish to thank Dr V. G. S. Damms for his help and co-operation and for allowing us to publish details of his patients, Dr J. G. Wallace for his work on the preliminary identification of the organism, and Dr Joan Taylor and Dr E. H. Gillespie for their helpful advice and criticism.