Objective: To evaluate reasons for using and not using alternative medicines. Methods: The cross-sectional study was conducted in 2009 on women over 18 years of age in Khorramabad, Iran. The subjects were selected by using cluster and simple random sampling method. The data were recorded in a questionnaire that involved questions about the subjects` age, marital status, their opinions on their general health, and advantages and disadvantages of conventional and alternative medicine. Results: Of the 1600 women initially selected, 1551(97%) represented the final sample. The mean age of the participants was 35.04±10.71 years. Overall, 435(28%) spoke of disadvantages of alternative medicine; 277(18%) about the advantages of alternative medicine; 523(34%) about the advantages of conventional treatments; and 316(20%) about the disadvantages of conventional treatments. The most prevalent reason for not using the conventional treatments was the cost factor in 159(50.3%). Trust in physicians 328(62.7%) and distrust in alternative medicine therapists 317(73%) were the most prevalent reasons for using conventional treatments and not using alternative medicine. Conclusion: Similar studies should be done on the reasons for using and not using each medication of alternative medicines separately.