We have measured the frequencies of micronuclei (MN) in adult male individuals living in areas of the Kerala coast, southwest India, with either high (HLNRA, >1.5 mGy/year) or normal levels of natural ionizing radiation (NLNRA, ≤1.5 mGy/year). Blood samples were obtained from 141 individuals, 94 from HLNRA and 47 from NLNRA, aged 18–72, and were subjected to the cytokinesis-block micronucleus (CBMN) assay. An average of 1835 binucleated (BN) cells per individual were scored. The overall frequency of MN (mean ± SD) was 11.7 ± 6.7 per 1000 BN cells. The frequencies of MN in the HLNRA (11.7 ± 6.6) and NLNRA (11.6 ± 6.7) were not statistically significantly different (P = 0.59). However, a statistically significant (P < 0.001) age-dependent increase in MN frequency was observed among individuals from both HLNRA and NLNRA. No natural background radiation dose-dependent increase in MN frequency was seen. MN frequency was not influenced by tobacco smoking or chewing but it was increased among individuals consuming alcohol. Chronic low-dose radiation in the Kerala coast did not have a significant effect on MN frequency among adult men.