Follow-up rates reported among longitudinal studies that focus on runaway adolescents and their families are relatively low. Identifying factors associated with follow-up completion might be useful for improving follow-up rates and therefore study validity. The present study explored how individual- and family-level constructs, as well as research project activities, influence the follow-up completion rate among runaway adolescents (N = 140) and their primary caregiver. Results showed that follow-up completion rates decreased as the number of research assistants (RA) assigned to each case increased and as participants' address changes increased. Additionally, among adolescents, more frequent alcohol use was associated with lower follow-up rates. The current findings suggest that researchers should (1) design their research so that one RA is assigned to each specific case, and (2) adjust their retention strategies to account for the differences in follow-up rates based upon the participants' drug of choice and residential stability.