Determining how many students drop out of school and why they leave is not easy. The definition of a "dropout" varies from school district to school district, and the mobility of students makes counting them accurately nearly impossible. In an effort to define dropouts in a way that can be applied uniformly across the country, a checklist has been devised which specifies eight common categories of students who can be described as dropouts. Equally important, specifications are given for students who should not be considered dropouts, such as truants, transferees, and returnees. Large margins of error occur in the national dropout rate because of widely varying ways of calculating dropout data. It is necessary to accept and apply uniform methods of defining dropouts and determining the dropout rate. Another area of concern is the identification and monitoring of students who are most at risk of dropping out of school. Offering these students special programs early in their school careers has proven helpful. Monitoring in terms of attendance, testing, and educational history will help to ensure positive progress for students as they proceed through school. Effective systems for identifying dropouts and at risk students are necessary for the accurate measurement of national educational progress. (VM)