Background: Second Hand Smoking is a significant public health problem that may be associated with serious health problems. Exposure to Second hand smoking may increase the risk of developing lung cancer, heart disease, intrauterine growth retardation and childhood asthma. Aim of the study: investigate the relation between women's knowledge and their exposure to second hand smoking in outpatient clinics at Woman Health Hospital. Subjects and methods: Descriptive Cross-sectional design was used. Quota sample of 700 women was participated. Tool: an interview questionnaire was used it included three parts: part one: socio- demographic characteristics, part two History of exposure to second hand smoking. Part three: Second hand smoking knowledge questionnaire. Results 73.3% of studied women were exposed to second hand smoking, 45.7% of them had poor knowledge about second hand smoking. Conclusion: The majority of participated women are exposed to second hand smoking at their homes also; more than one - third of them have poor knowledge regarding second hand smoking. Recommendations: Regular programs should be conducted to increase public awareness regarding effects of second-hand smoking through different mass media especially T.V.