As part of a large-scale survey of adolescent drug use in the State of New York, two absentee studies were carried out to estimate levels of drug use among school absentees. Students interviewed in households reported very little drug use. By contrast, absentees self-selecting themselves to participate in a group-administered questionnaire reported much higher illicit drug use than regular students from the same schools. However, comparison of students in the absentee sample with the total target absentee population, and the reverse association between drug use and selected background factors among absentees, suggest that most chronic absentees and heavy users, especially blacks and males, did not participate in the self-selected absentee sample. Attempts to identify factors related to higher drug use among absentees were unsuccessful. While poor school performance brings levels of illicit drug use among regular students to levels comparable to those of the absentees, poor school performances per se does not explain the higher rates of illicit drug use among the absentees. It is clear that school absentees who are generally excluded from school surveys are extremely hard to reach for research purposes.