Because passive smoke exposure has not been previously linked to diarrhea diseases in children, it was hypothesized that very young children exposed to environmental tobacco smoke (ETS) exposure at home would also be more likely to develop infectious gastroenteritis (GE) than their unexposed counterparts. During 1-year period, 260 children 36 months and younger were prospectively followed up in a private pediatric practice in a southern community in the United States. Multiple logistic regression analysis showed that ETS was strongly predictive of acute GE in the univariate analysis (P = .003). Even after controlling for the various confounders, ETS exposure was still significantly associated with acute GE (relative risk = 2.55; 95% CI = 1.26-5.18). It is speculated that, similar to acute respiratory infections, the same mechanisms may explain why ETS may also be associated with acute infectious GE.