Background: Hypertrophic cardiomyopathy (HCM) is a clinically heterogeneous genetic heart disease characterized by left ventricular hypertrophy in the absence of another disease that could explain the wall thickening. Elucidation of the genetic basis of HCM lead to the identification of several genes encoding sarcomeric proteins, such as MYH7, MYBPC3, TPM1, TNNT2, and TNNI3. Sarcomeric genes are mutated in approximately 40% of HCM patients and a possible explanation for the incomplete yield of mutation-positive HCM may be somatic mutations.Methods and Results: We studied 104 unrelated patients with non-familial HCM. Patients underwent clinical evaluation and mutation screening of 5 genes implicated in HCM (MYH7, MYBPC3, TPM1, TNNT2, and TNNI3) in genomic DNA isolated from resected cardiac tissue; 41 of 104 were found to carry a mutation, but as several patients carried the same mutations, the total amount of different mutations was 37; 20 of these mutations have been previously described, and pathogenicity has been assessed. To determine the effect of the 17 new mutations an in silico assay was performed and it predicted that 4 variants were damaging mutations. All identified variants were also seen in the DNA isolated from the corresponding blood, which demonstrated the absence of somatic mutations. Conclusions: Somatic mutations in MYH7, MYBPC3, TPM1, TNNT2, and TNNI3 do not represent an important etiologic pathway in HCM.