An analysis is presented of the total of 13 official surveys conducted between 1906 and 1979 of the number of disabled persons in the former German Reich and today's Federal Republic of Germany. The concept of disability was found to have been adapted to societal changes. From a helpless charge to be taken care of, the concept of the disabled changed into that of a person suffering from illness, to become that of the rehabilitee having a physical, sensory, mental, psychic, or educational handicap, who has a right to being accepted as a full and equal member of the community. As regards the method of data collection, the initial state surveys administered in an authoritarian manner (via official agencies) were followed by direct interviewing of those concerned; today the disabled are again registered via official agencies. All of the surveys are characterised by inconsistent use of almost any variable; this fact--besides the lack of comparability of the statistics with each other--warrants fundamental doubt in their usefulness as planning tools. In all surveys the number of disabled persons had been underestimated.