A number of physical problems which arise in the use of radium surface applicators of small area are considered from the point of view of radium and radiation distribution. Depth dose curves show the advantages of the use of larger radium skin distances, the improvement being particularly marked at the edge of the applicator. The effects of errors in radium distribution and radium skin distance are indicated. With a view to overcoming some of the difficulties, specifications of a number of standard small applicators are given.