The relationship between the expression of resistin in polycystic ovary syndrome (PCOS) and insulin resistance was investigated. The plasma resistin concentrations in 35 patients with PCOS and 40 controls were measured by ELISA. Luteinizing hormone (LH), follicle-stimulating hormone (FSH), and fasting insulin (FIN) were tested by radioimmunoassay. Insulin resistance index (HOMA-IR) was calculated. Fasting plasma glucose (FPG) was determined by oxidase test. West blot and reverse transcriptase PCR (RT-PCR) methods were used to detect the expression of resistin in adipose tissues.The levels of plasma resistin, LH, LH/FSH and FIN and HOMA-IR in patients with PCOS were sig-nificantly higher than those in control group (all P<0.05). Plasma resistin was correlated positively with FPG, FIN, HOMA-IR, LH and LH/FSH (r=0.56, 0.60, 0.65, 0.48, and 0.42 respectively). Resistin pro-tein and mRNA expression levels in patients with PCOS were significantly higher than those in normal tissues (all P<0.01). It was concluded that resistin might be involved in the pathogenesis of insulin re-sistance of PCOS.