Low socioeconomic status (SES) and exposure to passive tobacco smoke are associated with increased risk of smoking in adults, but the influences of these factors in earlier life periods on adult smoking behavior are not well understood. We investigated the relationship of SES and passive tobacco exposure over the lifecourse with adult smoking status in a multiethnic cohort of U.S. women (n = 262, average age = 41.8), using prospective data on maternal smoking during pregnancy and childhood SES, and follow-up data on current smoking, adult SES and household tobacco exposure. Low adolescent and adult SES consistently increased the risk of current smoking, but most associations were not statistically significant in multivariable models. Blue collar parental occupation at birth increased the risk of smoking, particularly for current smoking relative to former smoking (odds ratio [OR] = 2.7, 95% confidence interval [CI] = 1.2-5.9). After adjusting for SES, current and former smokers were more likely than never smokers to have exposures to prenatal tobacco (OR = 4.4, 95% CI = 2.1-9.4 and OR = 2.0, 95% CI = 1.0-4.2, respectively) and adult household tobacco (OR = 2.7, 95% CI = 1.3-5.8 and OR = 2.4, 95% CI = 1.2-4.8, respectively). Our results show that early life conditions have enduring influences on women's smoking behavior in middle adulthood, even after considering similar types of conditions in later life periods.