A case-control epidemiological study was conducted to determine whether an increased diagnostic rate for group A rotavirus in swine herds in Ontario was associated with specific management factors. The number of new herds tested per year and the proportion of new positive herds increased between 1994 and 1997. Herd size was larger and weaning age was younger in rotavirus-positive herds compared with rotavirus-negative herds. Pigs raised in all-in all-out nurseries were 3.4 times more likely to have a positive group A rotavirus diagnosis than pigs in continuous flow facilities. This study demonstrates that the changes seen in group A rotavirus disease herd status in Ontario are associated with changes in farm management practices, including farm expansion, early weaning, and all-in all-out production.