The age of onset was examined retrospectively in a group of severely asthmatic children. The mean age of onset for males was 29.4 +/- 22.7 months and 30.4 +/- 27.0 months for females. The distribution of age of onset between males and females was remarkably similar (X2 = 1.77, 0.6 less than p less than 0.9). The mean age of onset was similar in children not receiving corticosteroids compared to those children who were taking high and low dose corticosteroids. An early or late age of onset appeared independent of corticosteroid requirements. Children with five or more positive immediate skin tests had earlier age of onset and higher total serum IgE levels than those with four or fewer positive skin tests.