Like other health technologies, HTA should be judged on the quality and size of its effects. However, it is only in recent years that this aspect has received increased attention. A comprehensive theoretical analysis is still missing. In this article national and international studies on the influence of HTA reports are presented. On the basis of theoretical models, the thesis is developed that the potential of HTA reports is much more extensive and complex than has been generally assumed. In order to make use of this potential, a stepwise procedure is proposed, comprising the involvement of the groups concerned, the explicit inclusion of impact objectives in all HTA reports, and the subsequent evaluation of the effects produced. This procedure is illustrated by the example of one HTA topic.