The human MDR1 gene encodes for a P-glycoprotein (PGP), which acts as an efflux pump that transports a large variety of substrates from the inside of cells to the outside until protection against xenobiotics. The G2677T/A polymorphism in exon 21 is associated with PGP expression and function in humans. The present study was aimed to determine the frequencies of this polymorphism in a healthy population from Mazandaran province of Iran. A total of 120 unrelated healthy subjects from Mazandaran province, residing in Sari, coming for blood donating at Sari Blood Transfusion Center were enrolled. Genomic DNA was extracted from the peripheral blood lymphocytes of each subject. All subjects were genotyped for G2677T/A polymorphism by polymerase chain reaction-restriction fragment length polymorphism method. The genotype frequencies were G2677G (65%), G2677T (20.83%), G2677A (14.17%) and TT, AA, TA genotypes were not observed. Moreover, frequency of G allele (82.5%) was significantly (p ˂ 0.05) higher than the T (10.42%) and A (7.08%). This is the first study to investigate the G2677T/A polymorphism of MDR1 gene in population from Mazandaran province of Iran. These data may be relevant for dose recommendation of PGP substrate drugs and can help for individualizing drug therapy of organ transplantation and important diseases such as cancer and AIDS, congestive heart failure and etc.