Smoking has some undesirable effects on human health. Its effect on fertility is one of health problems, which public has little knowledge about them. Considering the prevalent of smoking between youth, we decided to assess the knowledge of women working in hospitals of Lorestan Medical Sciences University regarding the effect of smoking on fertility. This is a cross sectional study. 280 women were chosen so to assess the knowledge of women working in hospitals of Lorestan Medical Sciences University in 2001. Information were gathered through questionnaire which was prepared base on objectives of study and was used after proving to be valid. Results showed that 75.7% of women knew about respiratory disease, 79.1% knew about heart disease and 69.3% had knowledge about addictive effect of smoking. Base on results of this study, few women knew about fertility problem of smoking. Only 37.5% knew about infertility effect, 47% knew about intra uterine fetal death, 70.7% knew about spontaneous abortion, 52.1% knew about infant death and 10.7% had knowledge on early menopause effect of smoking. Therefore by increasing knowledge of women on effects of smoking, we can reduce the related effects.