Some forms of hypertrophic cardiomyopathy (HCM) are caused by mutations in cardiac sarcomeric genes, but environmental factors are believed to influence the hypertrophic response. A highly variable but potentially significant environmental factor is diet. Since soy-rich diets have been speculated to confer protection against cardiovascular disease, Stauffer et al. have explored the influence of a soy diet on cardiac growth and function in a transgenic mouse model of HCM (see the related article beginning on page 209). They report that mice fed a soy diet exhibited significantly worse HCM than mice fed a soy-free (milk protein) diet. This study provides the first evidence of an environmental modifier - diet - on the hypertrophic phenotype and has implications for the way in which disease phenotypes are assessed in genetically altered murine models of disease.