Evaluating new health care technology that is rapidly diffusing is one of the greatest challenges to researchers and policy-makers. If no evaluation is done until the technology is mature, evaluation will not influence processes of diffusion. If evaluation is done early, it may be irrelevant when it is completed because of developments in the technology and changing indications for its use. Nonetheless, early evaluation seems to be the only strategy possible to improve the integration of evaluation and diffusion. These difficulties are illustrated by the case of lasers. Lasers are diffusing relatively rapidly into health care, and yet few laser applications have been well-evaluated. Looking back over the past 20 years or so, only one public body, the National Eye Institute of the U.S. National Institutes of Health (NIH) seems to have tried to address the problem of laser evaluation. In the case of the Eye Institute, it has consistently identified new technologies for treatment of eye conditions and has mounted well-designed prospective evaluations aimed at influencing clinical practice. However, these evaluations have not been integrated with public policy-making, and therefore their influence has been relatively slow to develop. In recent years, concerns about technology have brought more active attempts to develop public policies to affect diffusion. Excimer laser treatment of coronary artery disease, especially as dealt with in the Netherlands, illustrates how a strategy can be developed. Regulation has allowed diffusion to be constrained while evaluation is carried out. Results of the evaluation will guide subsequent diffusion. In the future, such results will probably be used in determining if the laser treatment should be included in the benefit package of health insurance. A strategy for improving diffusion processes requires continuous monitoring of technological developments in health care to identify candidates for such early assessment. Since assessment resources are limited, setting priorities between candidates for assessment is necessary. Once priorities have been determined, an evaluative strategy can be formulated. As in the case of laser treatment of coronary disease a mechanism for constraining diffusion until evaluations are completed is necessary. Once the studies are completed, policy-making must be done promptly. The problem of successful implementation of this strategy lies with the public bodies, which are often not prepared to develop an integrated strategy of diffusion based on technology assessment and economic appraisal. Developing such a strategy, which would involve slowing diffusion in some cases and speeding it up in others, seems to have clear benefits. The field of medical lasers, and the broader field of minimally invasive therapy, seem to offer good opportunities to implement such a strategy.