Our aims, therefore, were as follows: (1) to analyze the association between the tag SNP CLOCK-rs4580704 and the incidence of T2D; (2) to analyze the association between the CLOCK-rs4580704 SNP and incidence of clinical CVD events depending on T2D status and; (3) to study whether a dietary intervention with the Mediterranean diet (MedDiet), very high in MUFA, within the framework of the PREDIMED trial, modulates these associations. This evidence concerns the gene CLOCK and type 2 diabetes mellitus.