Specific hypotheses regarding these factors which influence pediatric asthma hospitalization were tested in two different data sets: ecologic studies of trends and area variations of the children residing in the contiguous states of Maine, New Hampshire, and Vermont for 1980 - 1994; retrospective cohort analyses of children enrolled at a staff model HMO, Group Health Cooperative of Puget Sound for 1977 - 1994. These studies utilized detailed information regarding area and individual 'exposure' to differing systems of health care and asthma medications, controlling for socioeconomic status.