With the alarming increase in heart disease and heart failure, the need for appropriate and ethical animal models of cardiacdysfunction continues to grow. Currently, many animal models of cardiomyopathy require either invasive procedures or genetic manipulation, both of which require extensive expertise, time, and cost. Serendipitous findings at our institution revealed a possible correlation between sulfadiazine-trimethoprim (SDZ-TMP) medicated diet and the development of cardiomyopathy in IcrTac:ICR mice. We hypothesized that mice fed SDZ-TMP medicated diet continuously for 3 to 6 mo would develop cardiomyocyte degeneration and fibrosis, eventually leading to dilated cardiomyopathy. A total of 44 mice (22 Hsd:ICR (CD1) and 22 Tac:SW) were enrolled in the study. Half of these 44 mice were fed standard rodent diet and the other half were fed SDZ-TMP medicated diet. Baseline samples, including weights, CBCs, select biochemistry parameters, and echocardiography were performed prior to the start of either diet. Weights were obtained monthly and all other parameters were measured at least once during the study, and again at its conclusion. After 42 wk, mice were euthanized, and heart, lung and bone marrow tissue were submitted for histopathologic evaluation. Histologically, hearts were scored for the degree ofdegeneration, fibrosis, inflammation, and vacuolation. The data showed that SDZ-TMP did not have a significant effect oncardiac function, RBC parameters, biochemistry parameters (ALT, AST, calcium, magnesium, creatine kinase, and creatinine),hematopoiesis, or histologic heart scores. In addition, mice fed the SDZ-TMP medicated diet gained less weight over time.In summary, we were unable to reproduce the previous findings and thus could not use this approach to develop a novelmodel of cardiomyopathy. However, these results indicate that SDZ-TMP medicated diet containing 1,365 ppm of SDZ and275 ppm of TMP does not appear to have long-term detrimental effects in mice.