The purpose of this project was to develop and test culturally appropriate, low literacy, smoking cessation intervention materials designed to increase quit rates and prevent relapse postpartum for low-income African American and Hispanic women. A quasi-experimental, pretest-posttest design was used. Four Women, Infants, and Children (WIC) clinic sites in south and central Los Angeles were identified, pair-matched based on ethnic mix, and randomized to intervention (2 sites) or control status (2 sites). Participants were 18 years of age or older and either current or exsmokers (stopped smoking in the past year). The intervention group received the "Time for a Change: A Program for Healthy Moms and Babies" program including a 15-minute one-to-one counseling session and self-help guide, incorporating behavior-change strategies, booster postcard, and incentive contest. All materials were designed to match the cultural, language, and literacy needs of the target population. The smoking cessation intervention had a positive impact on both quit-smoking behavior during pregnancy and relapse prevention postpartum. Almost twice as many smokers in the intervention group (43%) reported quitting smoking at 9 months, compared to the control group (25%) (P < 0.01). At 6 weeks postpartum, 25% of the intervention baseline smokers were abstinent, compared to 12% of the control group (P < 0.01). Although no significant differences were observed for relapse during pregnancy among exsmokers at 6 weeks postpartum, a significantly higher proportion of intervention exsmokers were still abstinent (79%), compared to control exsmokers (62%) (P < 0.01). For the exsmokers, relapse prevention rates remained significant when adjusted for cotinine validated abstinence.(ABSTRACT TRUNCATED AT 250 WORDS)