The intragastric balloon prosthesis (PBIG) is being used as a mechanical treatment for obesity; an evaluation of its physiopathological implications, efficiency, and complications is still incomplete. In order to investigate in our area the incidence of complications of this endoscopic treatment, we have used the Danish model "Danish Obesity Treatment" (DOT) (Ballobes) inflated with air, in a prospective study in which forty obese patients were treated during three months. We draw the attention upon a gastric ulcer, a spontaneous anal extrusion-migration, and a duodenal ulcer. We establish the safety of the method, the literature is reviewed, we discuss the cause and treatment of these lesions, and we conclude indicating the low morbidity and the absence of major complications such as oesophageal perforation or intestinal obstruction occurring with other prosthesis models.