The authors reviewed asthma prevalence rates from all 501 Pennsylvania public school districts for 1997-1998 through 2002-2003. School nurses collect and report these data to the Pennsylvania Department of Health annually, and the data are aggregated by school district, county, and specified school year. The department initiated a descriptive pilot investigation in 2004 as part of the larger Asthma School Project, targeting all students with asthma in the two districts that had the highest and second highest asthma rates in Pennsylvania. The authors conclude that reporting of asthma by school nurses was a reliable data source, since most participating students had documentation of asthma diagnosis or asthma medication. The department also conducted environmental evaluations at the schools and investigated the occurrences of asthma exacerbations in participating students, but no unusual patterns or links to the schools were identified. The authors encourage other state health departments to consider designing and testing similar approaches to tracking asthma in students.