Genome-wide association studies (GWAS) in adults have identified single nucleotide polymorphisms (SNPs) associated with systolic blood pressure (SBP), but it is unclear whether the findings apply in youth. Further, the role of body mass index (BMI) in these associations is understudied. Our objective was to determine whether BMI modifies genetic susceptibility to high SBP in young people. The sample comprised 714 participants of European ancestry recruited in 1999-2000 from 10 Montreal-area high schools for a longitudinal study. SBP was measured at ages 12, 15, 17, 24, and 30. Blood and saliva samples were collected at ages 14, 20, and 25. Two evidence-based genetic risk scores (GRS) were constructed based on GWAS results in adults: GRS