Objective:To assess the efficacy and safety of the Chinese medicine Dingkun Pill(定坤丹, DKP) on insulin resistance in women with polycystic ovary syndrome (PCOS).Methods:A total of 117 women with PCOS were randomly assigned to Group A (38 women),Group B (40 women),or Group C (39 women) in a randomization sequence with SAS software and a 1∶1∶1 allocation ratio using random block sizes of 6,and were given 7 g of oral DKP daily (Group A),1 tablet of Diane-35 orally daily (Group B),or 7 g of oral DKP daily plus 1 tablet of Diane-35 orally daily (Group C).Patients took all drugs cyclically for 21 consecutive days,followed by 7 drug-free days.The treatment course for the 3 groups was continued for 3 consecutive months.Oral glucose tolerance tests (OGTT) were performed before treatment and again after 2 and 3 months of therapy,respectively,and homeostasis model assessment for insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI) were calculated.Results:Of 117 women with PCOS,110 completed the entire course of therapy:35 in Group A,36 in Group B,and 39 in Group C.After treatment,all three groups showed significant decreases in fasting glucose:at 1 h glucose decreased significantly in Group A (by 0.5± 1.4 mmol/L,P=0.028) and Group C (by 0.5± 1.2 mmol/L,P=0.045);while showing a tendency to increase in Group B (by 0.4± 1.9 mmol/L,P=0.238).HOMA-IR decreased significantly in Group C [by 0.5 (-2.2 to 0.5) mlU mmol/L2,P=0.034].QUICKI was significantly increased in Groups A and C (by 0.009± 0.02,P=0.033 and by 0.009± 0.027,P=0.049,respectively),while no change was observed in Group B.Repeated-measure ANOVA showed that the absolute changes in all parameters (except for glucose at 1 h),including glucose and insulin levels at all time-points during OGTr and in HbA1c,HOMA-IR,and QUICKI,were not significantly different among the 3 groups after treatment (P＞0.05).Conclusion:DKP or DKP combined with Diane-35 produce a slight improvement in insulin sensitivity compared with Diane-35 alone in PCOS patients.