Left ventricular hypertrophy (LVH) is a complex quantitative trait that has a strong prognostic value for cardiovascular mortality and morbidity. Cardiac mass is determined in part by the influence of genetic loci that are known as quantitative trait loci (QTLs), the localization of which can be performed experimentally in genetic animal crosses. The present chapter outlines standard procedures for the selection of appropriate animal strains, for assessment of mode of inheritance, for characterizing the cardiac phenotype, for performing whole-genome scans, and for conducting linkage analyses. Identification of QTLs may lead to the identification of candidate genes whose roles can be further investigated in either transgenic, knockout, or pharmacologically manipulated animal models.