Background: Studies on patient mobility have focused on patients who become lost-to-follow-up (LTFU). Much less is known about patients who move with a planned transfer of care from one HIV center to another. We assess disease progression in patients who moved and then returned to our care compared to patients remaining or were LTFU. Methods: We identified which patients left our HIV care program between 01/01/00-01/01/08, defined how they left (either moved or LTFU), and then determined the health status of returning patients. We examined the impact of the move on their health by comparing clinical measurements (e.g. CD4, new AIDS) at their departure and on return. Results: 44% of all patients left care; 38% of these returned. In contrast to those remaining in local care whose CD4 counts climbed, "moved" patients exhibited deterioration in both CD4 counts and incident AIDS comparable to LFTU patients. Only 1 in 3 patients who moved had our medical records requested by a new HIV center. Conclusion: We suspect that despite forward planning, a move may result in potential serious interruptions and/or disengagements of care. The potential harmful health effects can in some be equivalent becoming LTFU. Recognising and addressing the potential disruption in care from a planned move may be of value in improving outcomes.