During a 3-month recruitment period, a smoking cessation program was provided to all pregnant women who attended an HMO prenatal clinic and reported either that they were currently smokers (n = 35) or that they had quit at pregnancy onset (n = 23). Except for its in-clinic introduction, the behavioral smoking cessation program used a home-correspondence format with seven weekly mailings and a telephone answering system adjunct. At follow-up, all 23 women who identified themselves at baseline as self-initiated quitters reported continued abstinence from smoking. Urine thiocyanate assays confirmed these self-report data in 82% of the cases. Results of a multivariate analysis identified three factors--gravida, number of years a smoker, and number of friends who smoke--as significant predictors of self-initiated quitting. Of the 35 women who indicated that they were still smoking at baseline, 10 (28.5%) reported that they had stopped smoking at the time of the postprogram assessment. Available urine thiocyanate assays confirmed a nonsmoking status in all cases. The multivariate results indicated that four variables--gravida, severe nausea, baseline smoking rate, and spouse's smoking status--were significant predictors of quitting following exposure to the program. The majority of both self-initiated quitters and postprogram quitters reported that the program was useful in helping them to quit smoking and/or to remain abstinent over time. These results lend support to the viability of a home-correspondence, self-help program as a means for facilitating smoking cessation and continued abstinence from smoking during pregnancy.