This study looks at the role of dietary fat in 60 cats with chronic nonspecific diarrhoea from primary veterinary centres. Intestinal parasites, infectious diseases and non-GI conditions had been ruled-out. Fecal scores (zero = watery, 100 = very firm) were used by the owners for the evaluation of the diarrhoea at baseline and every day after the random assignation of a high fat (H = 23,2%) or a low fat (L = 10,5%) as the only treatment for 6 weeks. Twenty-eight cats on diet H and 27 on diet L completed the study. The diet therapy caused an improvement of fecal scores within the first week, a global improvement of the fecal scores of no less than 25 points, and a decrease in frequency of defecation. However, there were no differences between diets, suggesting that the level of fat in the diet has no importance in the management of chronic diarrhoea in cats.