CYP2D6, an enzyme, metabolizes a large number of commonly prescribed drugs. Variations in CYP2D6 gene encoding this enzyme have been associated with individual differences in drug metabolism rates. The purpose of our study was to identify some allelic variants of CYP2D6 gene and to detect defective CYP2D6 alleles, as part of a pharmacogenetic screening program.A prospective study was done on 120 participants referred to Royan Institute in 2013. Allele and genotype frequencies for polymorphism of CYP2D6 gene in exons 1 and 4 were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis and sequencing on PCR products, respectively.We identified a novel variant of the gene encoding cytochrome P450 2D6 (CYP2D6) at position +90 of intron 4 by sequencing method. This novel polymorphism of CYP2D6 has been deposited in GeneBank(®) under the accession number KF225465 in Jun 2013.In the current study, we identified novel polymorphism in intron 4. This single nucleotide polymorphism (SNP) is known as +90G>A in the fourth intron.