Human Cytochrome P450 3A4 is a major P450 enzyme in the liver and gastrointestinal tract. It plays an important role in the metabolism of a wide variety of drugs, some endogenous steroids, and harmful environmental contaminants. To investigate the interindividual variation in CYP3A4 levels we have carried out a study on the genetic polymorphism of 100 breast cancer subjects using fine needle aspiration cytology (FNAC) sampling procedure. DNA was extracted from all the samples and PCR was carried out for detecting the CYP3A4 gene polymorphisms. We selected exon-7 and 10 which are present on the 5'-flanking coding region of the gene using the respective primers for PCR followed by direct automated sequencing method for detecting the mutations. These mutations were compared to the wild type sequence structures obtained from GenBank database (accession no. AF209389). We found two novel point mutations which are heterozygous mutant alleles. The two variant alleles were Ile222Arg and Phe175Val occurring in coding region of exon-7. Ile222Arg mutation was found in 3 malignant cases whereas Phe175Val mutation was found in 4 malignant cases. This is the first report of these two novel point mutations in CYP3A4 gene. These mutations in the gene in respective patients were found to relate to drug response in invasive ductal carcinomas of breast cancer.