The occurrence of episodes of getting lost was examined in 104 subjects with dementia who were assessed every 4 months over 5 years. All subjects were initially living at home with a caregiver who could give good information. Forty-three subjects needed to be brought back home at least once. Five subjects repeatedly got lost. Forty-six subjects were kept behind locked doors at some point. Subjects who got lost were more likely to become permanently resident in institutions (odds ratio = 7.3; 95% confidence interval: 3.0 to 17.8). Patients who performed better on a behavioral test of topographical memory were less likely to get lost over the subsequent 5 years (negative predictive value: 90%). The risk of patients with dementia getting lost is substantial and requires frequent intervention by caregivers. This risk is a major reason for institutionalization. A simple test may help in assessing the risk of getting lost in patients with dementia.