The aim of this experimental investigation was to show whether immediate irradiation of a free flap or an island flap is dangerous or not. The free epigastric flap of the rat was used as a model for this investigation. The patency of the epigastric vessels of the rat was not influenced by the irradiation and the histological findings showed no early reaction to the irradiation of the vessels of the transplanted tissue. The vessels of this experiment indicate that a free tissue transplantation is possible even if a combined radio-surgical treatment is planned.