The U.S. Preventive Services Task Force is a prominent example of evidence-based medicine put to work. The Guide to Clinical Preventive Services and its Canadian counterpart distill thousands of articles into easily understood guidelines for the busy clinician. Rather than dictating practice, it provides the scientific base for prevention services. The second fundamental part of evidence-based medicine is the filtering of that evidence through the clinical skill of the clinician. Only the clinician can judge the applicability of the evidence and the preferences of the woman and her family. Some common preventive practices in women's health lack a scientific basis. Others clearly work. To maximize benefit, clinicians should emphasize and encourage prevention strategies that are effective. These include cervical cytology screening, blood pressure screening, urine cultures in early pregnancy, testing for phenylketonuria, and discouraging smoking. No health program can be reviewed in a vacuum. This is especially true in the managed care era. Clinicians must ask what benefit would have accrued had the same amount of time and money been spent on alternative programs. If practices with only a class C recommendation draw money and resources from other programs of proven worth (e.g., class A recommendations), then the former have a net negative impact on women's health. The Task Force report helps women, clinicians, payers, and policymakers make these important decisions.