The present article describes 94 patients (34 male and 60 female) with delusions of parasitosis, admitted to our dermatology clinic between 1978 and 1989. The female to male ratio was to one under the age of 45, and 1:2.1 over 45. The mean age of onset in males was 46.4 years, and in females, 52.8. In nine patients (6 male and 3 female), the delusions began shortly after their retirement, while in seven (1 male and 6 female) after separation from their families. The ratio of the number of patients living alone to that of patients living with their families was one to two, three times higher than that of the general population (1:6). About half of the patients had no skin lesions, while half the rest had excoriations. Three had eczematous lesions caused by the application of insecticides. In 58 patients, the creatures of delusion were mites. Most patients complained of some kind of cutaneous sensations of the skin, such as itching, tickling and prickling, while only two complained of auditory sensations. The color of creatures of delusion was black or white. Folie á deux was observed in 23 groups and affected both sexes.