We report three adult patients with gastrectomy who had malabsorption caused by Giardia lamblia. Type II gastrectomy had been carried out in the three patients several years before, and the clinical presentation was similar: chronic diarrhea with malabsorption. A remarkable fact was that the search for parasites in feces was repeatedly negative in two patients, the protozoon being identified in the intestinal biopsy samples. In the third case, the diagnosis was made by the visualization of Giardia cysts in the feces.