Our aim was to analyze risk of first hospital diagnosis of asthma in children (< 10 years) and adolescents (10 through 19 years) in Sweden between 1970 and 2004 by parental occupation, controlling for potential confounders. Data from the Multigeneration Register, in which all children born in Sweden from 1932 onward are registered with their parents, were linked to nationwide Hospital Register data. Standardized incidence ratios (SIRs) with 95% confidence intervals were calculated. A total of 47,019 first hospital diagnoses of asthma were recorded in children and 9,032 in adolescents. After accounting for age at diagnosis, sex, socioeconomic status, geographic region, parental history of a first hospital diagnosis of asthma, and period of diagnosis, 17 parental occupational groups were associated with increased risk of first hospital diagnosis of asthma in children and 9 with increased risk in adolescents. Seven parental occupational groups were associated with significantly increased risks in both children and adolescents: "nurses," "assistant nurses," "drivers," "chemical process workers," "cooks and stewards," "home helpers," and "building caretakers and cleaners." Significantly decreased SIRs were observed for those whose parents had higher socioeconomic status. We conclude that parental occupation affects risk of first hospital diagnoses of asthma in children and adolescents.