Summary.After GE or B II-anastomosis, an afferent or blind-loop syndrome is found in 0.5 to 20 %, as shown in the literature. There are several organic types and functional forms. Etiology, symptcmatology, diagnosis and therapy are discussed. In the acute form only immediate surgery is life saving. The smallest possible intervention should be preferred. In the chronic form, which depends upon the severity of the obstruction as well as its duration and may be associated with assimilation disturbances, the reconstruction of almost physiological conditions should be the aim. This means converting a B II-anastomosis to a B I-anastomosis with or without interposition of a jejunal segment.