The prevalence and predictors of wheeze syndromes, including asthma, were examined among 475 non-Hispanic (NH) white and 371 Hispanic pregnant women enrolled in a population-based study in East Boston, Massachusetts. Respiratory symptoms and risk factors were ascertained by questionnaire early in pregnancy. Hispanic and NH white women were of similar age (mean +/- SD, 26 +/- 5 yr), but Hispanics reported less schooling (30 versus 50% completed high school), a lower frequency of household pets (4 versus 47%), and a lower frequency of parental asthma (6 versus 12%). Hispanics smoked significantly less than NH whites did, both in prevalence (8 versus 50%) and number of cigarettes per day among current smokers (12 +/- 9 versus 22 +/- 10; p < 0.0001). Hispanics reported a lower frequency than NH whites did of doctor-diagnosed asthma (6 versus 12%), persistent wheeze (5 versus 19%), and either persistent wheeze or asthma (11 versus 30%). In multivariate analysis, active cigarette smoking and parental history of asthma were associated most strongly with wheeze syndromes. When these two factors as well as educational level, presence of household pets, and height2-adjusted FEV1 were controlled, Hispanics remained at lower risk of asthma (odds ratio [OR] 0.71; 95% confidence interval [CI], 0.37-1.37) and persistent wheeze (OR 0.48; 95% CI, 0.25-0.95) than NH whites. These results suggest that chronic wheeze syndromes are common among young urban women and are associated with both active smoking and a parental history of asthma. Hispanic women from Central and South America living in urban environments in the United States may be at less risk for these conditions than NH white women, in contrast to those from Puerto Rico.