Immunization data are collected annually from Illinois public and nonpublic schools. This report is a compilation of the data on the immunization status of school-age children in Illinois for the school year 1998-99. The compliance level for all Illinois students is 97.25 percent. The data by specific disease category, based on the percent of total student enrollment, reveal that no more than 1.17 percent of Illinois students were unprotected and in noncompliance in any of the 7 disease categories. Only 267 of the 4,130 schools reported compliance levels of less than 90 percent. Only 132 of 1,376 nonpublic schools reported compliance levels of less than 90 percent. An appendix summarizes student enrollment and compliance. (DFR)