Background: The aim of family planning is to prevent unwanted pregnancy. Using safe and effective contraceptive methods is necessary to achieve this goal. This study was conducted to determine the most causes of high application of unsafe contraception methods in Kashan city using a regression model.

 Materials and Methods: In a case control study 261 married women referring to health centers and using unsafe contraceptive methods (condom and withdrawal) were selected randomly. Also 261 women using safe methods (hormonal, ligation and intrauterine device) were selected as control group. Using multistage (cluster and simple random) sampling we collected data including age, job, educational level of women and their spouse, marriage duration, number of children, age of the last child and satisfaction about gender of children. The data were analyzed using Chi square and t-Student test in univariate step and then binary logistic regression at multivariate model.

Results: women's job and level of education, men's age and level of education, duration of marriage and number of children were statistically associated with unsafe contraception application. In the final regression model, women's job (OR=2.241) and age (OR=1.725), duration of marriage (OR=1.074), number of children (OR=0.341) and age of the last child (OR=1.544) were the most important determinants of unsafe contraception.

Conclusion: To decrease the application of unsafe methods it is suggested that educational programs should be reinforced for women who have a job, less than 3 children, longer marriage and are older than 35 years old and their last child is older.