Despite growing research interest in co-occurring psychiatric and substance misuse disorders, relatively few longitudinal studies have been conducted with dual diagnosis populations. Many of the longitudinal studies that have been done have experienced excessive attrition. Thus, investigators have noted that one of the primary difficulties of conducting longitudinal studies with this population is successfully minimizing attrition during follow-up. This study, conducted in 1991 1993, describes retention and tracking methods employed in a longitudinal study of 485 dual diagnosis participants. Follow-up interview completion rates at the 2-, 6-, 10-, 14-, and 18-month interviews were 86.7, 85.6, 85.1, 84.5, and 88.4%, respectively. Several case studies are provided that document some of the challenges facing project staff and successful strategies for handling them. A notable finding from this study was that participants reported that the relationship established with the interviewer was more important than material incentives in preventing study attrition.