Abstract: Objective To investigate the association between occupational physical activity,body mass index(BMI)and uterine leiomyoma(UL)in middle aged and elderly women.Methods A hospital-based case control study was conducted.Totally 353 UL patients aged 35-62 years were selected as cases from the First Affiliated Hospital and the Third Affiliated Hospital of Liaoning Medical College and Jinzhou Women and Children's Hospitial.The controls(n=353)were patients suffering from diseases not related with UL.All subjects were interviewed using a structured interviewer-administrated questionnaire.The height and weight of the subjects were measured simultaneously.Then physical activities were investigated using International Physical Activity Questionnaire(IPAQ).The odds ratios(OR)and their 95% confidence intervals(95%CI)of UL for occupational physical activities and BMI were estimated with multiple logistic regression model.Results Socio-demographic characteristics(age,marital status,educational level,and familial income)were not significantly different between the two groups(P>0.05).However,the percentage of controls(34.28%)with number of live births ≥2 was significantly lower than the cases(44.19%)(P=0.026).Moderate occupational physical activity could decrease the risk of UL(OR=0.679,95%CI:0.480-0.925;P=0.007).Compared with the subjects with normal BMI,both overweight and obesity had higher odds of UL(OR=1.571,95%CI:1.053-2.182,;P=0.001;OR=1.875,95%CI:1.191-2.774;P=0.002,respectively).Moderate occupational physical activity could decrease the risk of UL in the subjects with normal BMI(OR=0.455,95%CI:0.215-0.960;P=0.039).After adjustment for multiple potential confounders,the results remained unchanged.For the subjects with higher BMI(24.00-27.99 kg/m²),the OR in third quartile of metabolic equivalents was 0.389(95%CI:0.182-0.832,P=0.015)compared to the lowest quartile.Conclusion Moderate physical activity and normal BMI can contribute to lower incidence of UL.