Information on oesophageal, duodenal and rectal atresias was collected from the hospitals, malformation register and death certificates in Finland from 1970-79. The respective prevalence rates were 4.1, 1.4 and 3.6 per 10,000 births, which are among the highest rates cited in the literature. Mothers of children with oesophageal and duodenal atresias were older than the average for child-bearing women in Finland. The sex ratio (male/female) of rectal atresia patients was 2.4. About 50% of the atresia patients had associated malformations. The data indicated time-spaced clustering for atresias. Furthermore, the cases of oesophageal and duodenal atresias appeared to spread within a time period of 30 days from a province to its neighbouring provinces to the north. Spreading was not observed for rectal atresias but clustering was noted when smaller geographic areas and individual communities were analysed. Occupations involving animal contacts were overpresented among the fathers of atresia patients. The data suggest infective aetiology, probably with no known clinical symptoms and no seasonal patterns.