A report is presented of 319 unselected patients investigated by the method of plate thermography according to Tricoire, which is a comparatively new method in the diagnosis of breast cancer. 281 cases were additionally examined by mammography and those cases in whom malignancy was suspected underwent further cytological and histological investigation. The results of plate thermography and mammography are compared. The high degree of diagnostic accuracy achieved in the present series of cases by the use of plate thermography indicates that this procedure is not only a valable adjunct in the diagnosis of breast cancer but, moreover, seems to be recommendable as a screening method.