Ancylostoma caninum, the cosmopolitan canine hookworm prevalent in domestic pets throughout northeastern Australia, has been identified as a cause of obscure abdominal pain. To investigate the influence of climate on putative and confirmed human infections, a retrospective study of patients with eosinophilic enteritis and established infections was undertaken to identify the monthly and seasonal rates. The numbers seen each month were maintained throughout most of the year but decreased in June and remained low during winter. An increased rate of enteritis occurred during spring, which preceded the wet season. It is concluded that climate directly influences the rate of human enteric infection by canine hookworms. The increase in prevalence before the monsoon season was unexpected and suggests other influences, such as extraneous infection promoted by the irrigation of domestic gardens and possibly endogenous reinfection of the gut by hypobiotic larvae.