During the last 2 decades, we have gained new insights into the pathogenesis of asthma; consequently, new therapeutic agents and approaches to therapy have emerged. Nevertheless, significant gaps remain in our understanding of this disease. Important new treatment issues affect childhood (the usual time of asthma onset), and researchers have recently described increases in asthma incidence in children. Yet, most clinical studies have been performed with adults, and our knowledge about major determinants of childhood asthma remains incomplete. Major challenges in pediatric asthma include methods of easily assessing lung function and noninvasive methods of assessing asthma's inflammatory nature. Research that addresses the mechanisms responsible for disease onset is also critical to decrease the prevalence of asthma. What we know about adult asthma cannot be used in the treatment of children without further study, but it is now clear that effective treatment should begin during childhood.