The influence of orally administered fosfomycin on intestinal disaccharidases in albino rats was studied. The enzymes were evaluated in a homogenate of the intestinal mucosa, using the method of Sols and de la Fuente which is based on the colored reaction of the glucose that is freed by the disaccharidases from disaccharides with a glucose-oxidase-peroxidase reagent and a chromogen (Glucostat). The results obtained in animals treated with a daily dose of 1 g/kg fosfomycin for 6 consecutive days are compared with the corresponding results of animals that received 1 ml/day of saline solution during the same period. Our conclusion was that fosfomycin has no effect on the intestinal disaccharidases in rats.