This article addresses several questions about the effect of disenrollment on the start-up phenomenon in health maintenance organizations that were raised in a recent exchange of articles and comments in this journal. The results show that disenrollees, like continuous enrollees, go through a start-up phase of utilization that decreases over duration of membership to a stable lower level. The study also differentiates between voluntary and involuntary disenrollees, both of which go through start-ups. The different characteristics of the start-ups of both groups of disenrollees are contrasted with those of continuous enrollees. The implications of these findings for planners and administrators are discussed, and a future research agenda is recommended.