['To determine if impulsivity and socio-economic status (SES) interact to influence gambling onset in youth.', 'Longitudinal study of grade 7 students followed for 8 years.', 'Montréal, Canada.', 'A total of 628 adult students aged 12.6 years on average at cohort inception.', 'Impulsivity and SES (parent education, area deprivation) were collected during secondary school. Age of gambling onset was collected retrospectively when participants were aged 20.3 years. Cox proportional hazards regression was used to model the association between time to first report of gambling and interaction terms for each of impulsivity and parent education, and impulsivity and area deprivation accounting for sex and ethnicity.', 'Median (interquartile range) age of gambling onset was 17.0 (4.0) years. Impulsivity independently increased the risk of gambling onset among participants with no university-educated parent [hazard ratio (HR) 1.3; 95% confidence interval 1.1-1.5] and those living in highly deprived areas (HR 1.7; 1.5-2.0). Impulsivity was not associated with gambling onset among high SES youth. Among participants with high impulsivity, risks were elevated for those with no university-educated parent relative to one or more university-educated parent (HR 1.7; 1.1-2.7), and for participants living in deprived relative to advantaged areas (HR 5.0; 2.6-9.6). SES was not associated with gambling onset among participants with low impulsivity.'] Do impulsivity and socio-economic status interact to increase the risk of gambling onset among youth?