A polymorphism in the HMGCR gene (rs17238540) was related to a lower response to pravastatin treatment and we aimed to investigate whether an interaction is present for this polymorphism on blood pressure (BP) and salt intake. Cross-sectional urinary sodium and potassium concentration and the polymorphism were assessed in a large population study. Participants with the mutated allele (G) had significantly higher BP than homozygous TT. There were highly significant positive trends between BP and urinary sodium:potassium ratio across quartiles in men, with less effect in women, especially women carrying the mutated allele, G. Multivariate regression showed a significant positive association between BP and the urinary sodium: potassium ratio that differed in men and women according to genotype. In men carrying the G allele, the regression slopes for diastolic BP and systolic BP were higher than in men TT and the opposite was observed in women. Our results suggest that the SNP rs17238540 in the HMGCR is associated with the BP response to urinary sodium: potassium ratio, the magnitude of the association differing according to possession of the G allele.