BACKGROUND: Currently, little is known about argileh (water pipe or hubble-bubble) and cigarette smoking among pregnant women in the Arab world, despite emerging evidence on the adverse health effects of argileh smoking and well-established knowledge about the health risks of cigarette smoking during pregnancy. OBJECTIVES: The present study assesses pregnant Arab women's knowledge of chemical contents and related harmful effects of argileh and cigarettes, their attitudes towards smoking argileh and cigarettes, and their actual smoking of argileh and cigarettes, both before and during pregnancy. METHODS: A stratified sample of 864 women from 23 health care centers in Lebanon completed a structured, interviewer-administered questionnaire. Information was collected on basic demographic variables, women's knowledge, attitudes, and cigarette and argileh smoking. RESULTS: Women were partially knowledgeable about the health risks of cigarette smoking, knew little about the harmful ingredients of argileh smoking, and had many misconceptions regarding how argileh worked or how it can produce harm. Attitudes were permissive towards all forms of smoking. Almost one quarter (23%) of participants reported smoking during pregnancy, with 17% smoking only cigarettes, 4% smoking only argileh, and 1.5% smoking both cigarette and argileh. CONCLUSION: A significant and growing percentage of pregnant Arab women are smoking in Lebanon, with four cigarette smokers for every argileh smoker. Smoking behaviors are empirically linked with important gaps in knowledge and with permissive attitudes. These data may be used to design more effective prevention programs targeting this vulnerable population.