GSTM1, one of the mu type glutathione-s-transferase isozymes in human, has been observed to be inherited dominantly, and the polymorphism of this gene can be detected by polymerase chain reaction (PCR). In this report we have determined the frequency of a homozygous deletion mutation of the GSTM1 gene in some populations of the Sundergarh District in Orissa, India. About 24% of unrelated individuals (n = 72) were detected to carry this deletion mutation in homozygous form. Possible implications of this homozygous deletion are discussed.