There are few reports in the literature concerning non-union of Colles' fractures or its treatment. We describe two cases in which the fractures had been treated in the standard manner by reduction and plaster immobilisation for six weeks. The wrists of both patients were mobilised free of external support for several months before the complication of non-union was diagnosed. A simple radiographic technique for the diagnosis of non-union is described, using flexion and extension views of the wrist, and a method of treatment is outlined.