Healthy subjects received a diet with a constant content of protein, fat, minerals and vitamins. To this diet were added increasing amounts of fat in the form of corn oil and olive oil up to a maximum of 639 g/ die per os. The excretion of free fatty acids, neutral fat, and nitrogen with the faeces was examined. Under the extremely high oral fat load the fat utilization differred individually and amounted to more than 98 % during 20 days with a supply of 639 g of fat/die. A positive correlation between the amount of fat ingested with the diet and the amount of fat excreted with the faeces was detected. – Furthermore, the time when abdominal disturbances and diarrheas appeared was individually different. One subject tolerated 500–600 g of fat without corresponding symptoms. A pronounced tendency to sweat resulted regularly from a daily fat amount of 300–400 g.