After a fatal case of invasive group A streptococcal disease, serotype T-1, in a child care centre, group A streptococcal T-1 prevalence was measured and risk factors for carriage were determined. A total of 87% (224/258) had throat culture tests. Group A streptococcus was isolated from 57 (25%), and of the 50 isolates serotyped, 38 (76%) were T-1. Group A streptococcal T-1 prevalence was 18% (38/217) and six of nine rooms had children with group A streptococcal T-1 isolates. The risk of group A streptococcal T-1 carriage was increased for children who shared the index case's room (odds ratio (OR) = 2.7; 95% confidence interval (CI) = 0.8 to 9.4) and for each additional hour per week in child care (OR = 1.03; 95% CI = 1.001 to 1.061); and decreased in children taking antibiotics in the preceding four weeks (OR = 0.2; 95% CI = 0.1 to 0.9). Carriage of the invasive group A streptococcal strain could not be determined by identified risk factors alone.