Pleomorphic virus-like particles which resemble coronaviruses in morphology were found in faecal specimens from Aboriginal and non-Aboriginal children in Western Australia. They were equally prevalent in those with or without symptoms of diarrhoea. A much greater proportion of Aboriginal than non-Aboriginal children were found to be excreting the particles. The proportion of children who excreted the virus-like particles increased with age. Coronavirus-like particles, indistinguishable from those found in humans, were found in a number of Aboriginals' dogs.