The frequency of chromosomal aberrations (CA) in peripheral blood lymphocytes of dilated cardiomyopathy (DCM) patients was used to evaluate the extent of DNA damage and genomic instability. Blood samples were collected from 48 DCM patients of an equal number of age and sex matched controls from the Vellore region of South India. A significantly higher number of chromosomal aberrations were observed in the patient group as compared to the controls (p<0.001). To the best of our knowledge, this is the first report where DNA damage was estimated using the frequencies of CAs in the peripheral blood lymphocytes of dilated cardiomyopathy patients. The observation showed that it was desirable to apply CA analysis, which could be used as a biomarker for validation.