This essay is in two parts. The first section contains information about teacher aides, based on experience in the United States and Canada. Aides are becoming increasingly popular in both countries. Their effect on schools is generally to allow a redistribution of teacher time, to increase teachers' job satisfaction, and to increase teacher effectiveness slightly. They also tend to stimulate cooperativeness. Training programs for aides are becoming common in the U.S., but they do not generally make formal provision for teacher associations to participate in planning. This section concludes with a brief statement of the case for including teacher aides in professional associations in some form of affiliate membership. The second section discusses the implementation of the policy, based on a theory of change processes. It concludes that although a membership policy of affiliation for aides would involve substantial opinion change and careful and committed leadership by a change agent, few practical difficulties would be likely to arise. (Author/RT)