This study examined the relationship of age at asthma diagnosis to the subsequent impacts of 12 common asthma triggers, which we classified as either mainly physically based or strongly psychosocially mediated. The physically based triggers were air pollution, cigarette smoke, high humidity, high/low environmental temperature, allergy problems, respiratory infection, physical activity, and nighttime hours; the psychosocially mediated triggers were stress or worry, anger, excitement, and laughter. Data were collected with questionnaires from families with asthmatic children (n=115), 2 to 20 years of age, as part of a larger study of biological and psychosocial factors in asthma and other illnesses. Using parents' reports, we classified the children as early-diagnosed (before age 2) or later-diagnosed (at or after 2) for asthma and compared these groups, separated by gender, in 2 x 2 multivariate analyses. The impacts of all four psychosocially mediated triggers on asthma attacks were significantly greater for the later-diagnosed children than the early-diagnosed children. No age of diagnosis differences were found for any of the physically based triggers, and no gender or interaction effects were found for either type of trigger.