Cockroach-specific IgE antibodies (CR-IgE) were assayed in the sera of 51 asthmatic and 33 healthy, nonallergic children. Cockroach IgE was detected in 43 asthmatic children (84%), seven of whom showed a high CR-IgE response (> or = 1.5 IU/ml). Only three of the healthy children (9%) had a positive response, and none of them were in the strongly positive category. The difference from the asthmatic group was statistically significant (P < 0.001). Children with clinically mild asthma had a significantly lower CR-IgE positivity rate than moderate and severe cases. The presence of other allergic manifestations or family history of atopy had no relationship to CR-IgE, nor did the residency, age, duration of illness, or total serum IgE levels. However, the CR-IgE titres were positively correlated with the absolute eosinophil counts. Thus, cockroach antigens are common inhalant allergens in Egyptian asthmatic children.