Little insight is available in the literature on how best to assist the pregnant smoker in public health maternity clinics to quit during pregnancy. A randomized pretest/posttest experiment was used to evaluate the effectiveness of two different self-help cessation methods. Three hundred and nine pregnant women from three public health maternity clinics were assigned randomly to one of three groups with one-third assigned to each: a control group; a group receiving the American Lung Association's Freedom From Smoking Manual; and those receiving A Pregnant Woman's Self-Help Guide to Quit Smoking. Using a saliva thiocyanate (SCN) and behavioral report at mid-pregnancy and end of pregnancy to confirm cessation or reduction, 2 per cent in the control group quit and 7 per cent reduced their SCN levels substantially. Of the women assigned to the ALA method, 6 per cent quit and 14 per cent reduced their SCN levels substantially. Of the women who used the Guide, 14 per cent quit and 17 per cent reduced their SCN levels substantially. Results of this trial indicate that health education methods tailored to the pregnant smoker are more effective in changing smoking behavior than the standard clinic information and advice to quit and/or the use of smoking cessation methods not tailored to the needs of the pregnant smoker.