A 30 month survey of patients suffering from diarrhoea in Northern Tasmania revealed that Cryptosporidium sp. could be detected in 2.4% (81/3405) of stool specimens examined. This study on Cryptosporidium provides the first data to shed some light on its epidemiology and association with diarrhoea in Tasmania. The study indicates that cryptosporidiosis in Tasmania has a particularly high prevalence in children, is more common in Spring and Autumn and that infection is often associated with animal contact or the drinking of unpasteurized milk.