A systematic search for cases of Creutzfeldt-Jakob disease occurring in the ten-year period 1968 through 1977 was conducted in the city of Paris and surrounding departments which comprise the greater Paris area. Fifty-six cases were found among the total population of approximately 10 million inhabitants, with a maximum incidence of 1.1 cases per year per million people in the densely populated city of Paris and a progressively lower incidence in the less heavily populated suburban and rural areas of the region. There was no temporal or geographic clustering of disease. Attention is drawn to the often rapid onset and short duration of illness (nearly two-thirds of the patients died within five months of onset) and the frequent early occurrence of symptoms such as asthenia, diaphoresis, and disturbances of sleep and appetite.