Fecal microbiota transplantation (FMT) is a novel strategy for the therapy of dysbiosis-associated disorders via modulation of the gut microbiota. Intestinal dysbiosis is associated not only with digestive disorders, but also with a variety of extra-digestive disorders. A worldwide increasing number of FMT can be expected in the future as well as an increase in adverse events. We describe the case of a patient with chronic radiation colitis that developed adhesion ileus 2 days after FMT. Since these problems never occured before and the short time interval favours a causality, we speculate about FMT-induced alterations in gut motility causing a "trapping" of the small intestine in an adhesion and other mechanisms beyond "pure" coincidence.