Abstract： Objective To clarify the relation between the C3435T polymorphism of multidrug resistance 1 (MDR1) gene and human refractory epilepsy (RE) in ethnic Han Chinese. Methods We collected 170 patients with epilepsy, whose diagnoses were correct and treatments were reasonable. RE was defined as having uncontrolled seizures that occurred with an average frequency of at least once a month for a period of at least 2 years; during the 2-years period, at least 2 different antiepileptic drugs (AEDs) were used daily, either singly or in combination. According to the definition, 91 patients were classified into RE group and the other 79 patients into non-RE group. A 5-mL venous blood sample was taken from the patients for DNA extraction and genotyping. Genotype of C3435T polymorphism in MDR1 gene was determined by polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP). Results The distribution of CC, CT, TT genotypes was 48.4%, 40.7%,11.0% in RE group, and 40.5%, 38.0%, 21.5% in non-RE group, respectively; no significant differences of C3435T genotype were noted between the 2 groups (x2=3.615, P=0.164). The C and T allele frequencies were 68.7%, 31.3% in RE group, and 59.5%, 40.5% in non-RE group, respectively; no significant differences were found between 2 groups (x2=3.112, P=0.080). Patients were divided into primary epilepsy group and cryptogenic or symptomatic epilepsy group according to the etiology;analyses of the genotype and allele of C3435T in the sub-groups (RE and non-RE subgroups) of this 2 groups were similarly unremarkable. Conclusion No association between the C3435T polymorphism in MDR1 gene and RE in ethnic Han Chinese is noted.