Among inner-city children with asthma, cockroach allergen exposure has been associated with allergic sensitization.We hypothesized that cockroach allergen levels in homes would be associated with sensitization to cockroach allergens in children.From a low-income preschool program, 341 four-year-old children selected on the basis of the willingness of their caregivers to participate in the study were enrolled. Dust from their beds and kitchens were analyzed for cockroach (Bla g 2), mouse (mouse urinary proteins), and cat allergens (Fel d 1). Serum samples were analyzed for allergen-specific IgE antibodies by immunoassay.Bla g 2 levels >1 U/g in children's bed and kitchen dust samples were independently associated with cockroach-specific IgE (odds ratio [OR], 2.7; 95% CI, 1.1-6.4; and OR, 3.4; 95% CI, 1.2-9.4, respectively), adjusting for sex, ethnicity, asthma, pet ownership, mother's allergic sensitization, environmental tobacco smoke, and having lived in other homes. Bla g 2 was associated (OR, 3.6; 95% CI, 1.0-13.1) with cockroach-specific IgE among children with asthma. Among children without asthma, the ORs were similar (OR, 3.0; 95% CI, 0.9-10.3), but the association was not statistically significant.Concentrations of the major cockroach allergen, Bla g 2, in settled dust were associated with cockroach-specific IgE independent of other factors in a cohort of 4-year-old inner-city children.