So far all calculations of the number of demented people are based on rates from meta-analyses, mean rates of meta-analyses or spatial analyses. This article presents age- and gender-specific prevalence and incidence rates of dementia that are based on a large sample of the German Sick Funds (Stichprobendaten von Versicherten der gesetzlichen Krankenversicherung (GKV)) with 2.3 million people from the year 2002. Prevalence rates increase from 0.8% and 0.6% for 60-64 year old men and women to 30% and 43% for men and women aged 100 or older, respectively. Incidence rates increase from 0.18 and 0.14 cases per 100 person-years for 60-64-year old men and women to 9.9 and 10.9 for over 95 year old men and women, respectively. Our results confirm rates from earlier studies on the basis of meta-analyses. Regional differences show for the first time that higher prevalence rates exist for East German women and men above age 85. In 2007 about 1.07 million moderately or severely demented people live in Germany of which about 244 000 are incident cases when we extrapolate our rates to the population of this year.