Campylobacter infection has one of the highest rates of all the notifiable diseases in Australia, with a peak in children aged 0–35 months. A matched case-control study was conducted to investigate risk factors for campylobacter infection for children in this age group. Eighty-one cases and 144 controls were enrolled in the study that was conducted between 24 January 1996 and 21 January 1997. The following risk factors were found to be independently associated with illness: ownership of pet puppies (adjusted odds ratio [OR] 16·58, 95% confidence interval [CI] 3·73–73·65) and pet chickens (OR 11·80, CI 1·37–101·75), and consumption of mayonnaise (OR 4·13, CI 1·61–10·59). We propose that children aged less than 3 years are at risk of campylobacter infection if residing in a household which has puppies or chickens as pets.