While technology assessment is seen as a mechanism for achieving effective and efficient use of health care resources, it has not as yet made the impact on policy decisions that its potential would suggest. Considerable barriers have been encountered in translating assessment results into policy concerning the adoption and use of technologies, with 'political' factors often being decisive. This paper places technology assessment in the content of the policy process to clarify both (a) how conflicting interests and organizational features can often hinder the selection of optimal policies, and (b) the potential roles technology assessment could nonetheless play. The resulting framework is termed the 'rational-political' model of policy development. The paper uses the example of policy making about the regulation of biotechnology, drawing on information from a survey of decision-makers (n = 561) involved in issues concerning the development, approval, and payment for pharmaceutical products.