In the San Antonio Heart Study (SAHS) we investigated the effects of exposure to parental smoking on diabetes, hypertension and the metabolic syndrome in adult offspring aged 25-64 years.In a retrospective cohort study the parental smoking status during childhood, obtained through a postal questionnaire, determined a person's exposure status. Logistic regression models were used to calculate odds ratios for diabetes, hypertension and the metabolic syndrome at the baseline SAHS examination in relation to parental smoking status. All models were adjusted for age, sex, ethnicity, education years, personal smoking status (current, former or never-smoker), BMI and, in the case of diabetes, a family history of diabetes.Of the 2,371 participants who returned the mailing, 44.5, 5.4, 20.0 and 30.1% reported that their father, mother, both or neither parent smoked, respectively. Participants reporting that both parents smoked were 1.60 (95% CI: 0.95-2.69) times more likely to have diabetes, 1.55 (95% CI: 1.05-2.28) times more likely to have hypertension, and 1.46 (95% CI: 1.01-2.10) times more likely to have the metabolic syndrome than participants reporting that neither parent smoked during their childhood. Odds ratios, after limiting the population to younger participants (i.e. <or=50 years) to reduce survivor bias, were 2.53 (95% CI: 1.21-5.31), 1.29 (95% CI: 0.78-2.16), and 1.41 (95% CI: 0.89-2.22) for diabetes, hypertension and the metabolic syndrome, respectively.These results provide evidence that early exposure to parental smoking may be associated with an increased risk of diabetes and perhaps hypertension and the metabolic syndrome.