Prevention has potential benefits, but the majority of people undergoing disease screening will receive no benefit and may actually be exposed to health risks. Public opinion is generally very favorable toward prevention. However, many recent guidelines recommend fewer preventive services in women than previously suggested. New recommendations are to wait until 50 for mammography screening, to screen only every other year, and to not teach self breast examinations. Papanicolaou tests for cervical cancer screening are recommended to be done less often (every 2-3 years) and to be started later than previously suggested (not before age 21). Screening for ovarian cancer is not recommended. Guidelines suggest avoiding hormone therapy for primary prevention of coronary heart disease, not giving aspirin to prevent myocardial infarctions in women, and not screening women without risk factors for hyperlipidemia. These recommendations have caused confusion and, because of being revealed during a national health reform debate, have even been perceived as "rationing care." Others see them as "rational care," because they encourage utilization of beneficial services while discouraging use of those that may lead to more harms than benefits. Development of prevention guidelines requires value judgments, so despite the use of evidence, these recommendations have not all achieved widespread support. Understanding the data behind the guidelines, health care providers can decide how to approach prevention in practice, taking into consideration individual patient risk factors and preferences.