The Miami Structured Interview--1 was developed (1) to assess Type A behaviour in a broader age range of children than tested with previous interviews, and (2) for cross-cultural studies. This study examined the validity of the Miami Structured Interview--1 for assessing Type A behavior in 507 American and Greek preadolescent (ages 7-11) and adolescent (ages 12-16) boys. The interview was scored on voice stylistics such as speed of speech, word emphasis, and latency of response. Validity was tested using the Matthews Youth Test for Health (MYTH), a teacher rating scale of Type A behaviors. Interview determined Type A's received significantly higher MYTH scores than non Type A's for American adolescents (p less than 0.05), Greek preadolescents (p less than 0.01), and Greek adolescents (p less than 0.05). The interview also identified extreme groups of Type A's and Type B's for American adolescents (p less than 0.01) and Greek preadolescents (p less than 0.05). The findings support the cross-cultural validity of the Miami Structured Interview--1 and the Type A construct for children. Limitations of the Miami Structured Interview--1 are discussed.