The goal of this study was to describe the evolution of dementia severity in a very old dementia population. We investigated a representative group of demented subjects gathered from a population-based study (n = 223). Changes in cognition, functioning, and performance on global scales were followed over a period of 7 years. At baseline, 19% of the demented subjects were found to be severely impaired according to the Clinical Dementia Rating scale, 41% according to the Mini-Mental State Examination score, and 31% according to Katz activities of daily living scale. After 7 years these proportions were 78%, 93%, and 68%, respectively. The probability of surviving 3 years, 5 years, and 7 years after baseline examination was 48%, 28%, and 15%, respectively. Over a 7-year follow-up period, subjects suffering from questionable-mild dementia had a mean survival of 3.9 years (95% confidence interval 3.3-4.5), whereas subjects with severe dementia survived on average 2.9 years (95% confidence interval 2.5-3.2). Male gender, lower education, and poor cognitive and functional status were associated with shorter survival in milder cases, whereas the only factors that predicted shorter survival in more severe cases were older age and poor functional status. Long-term survivors in dementia are not rare, and as the absolute number of demented people is increasing, expanding our knowledge of these persons is of high public health importance.