It is estimated that in the year 2007 more than 1.4 million individuals in the United States will be newly diagnosed with invasive (non-skin) cancer [1,2]. The lifetime risk of developing cancer is approximately I in 2 for men and I in 3 for women [1]. The risk of developing cancer increases with age, with more than 75% of cancers diagnosed in persons aged 55 years and older [1]. Cancer is costly, with more than $206 billion spent in 2006 in direct and indirect costs [1]. Cancer also has a major impact on an afflicted individual's quality of life and is the second most common cause of death in the United States. One in four deaths in the United States is caused by cancer; nearly 560,000 Americans are expected to die of cancer in 2007 [1,2]. As a disease entity, cancer is an important condition for patients and primary care physicians. Primary care physicians are crucial in the "war" against cancer [3]. Studies have shown that having a primary care physician is associated with a higher rate of early breast, cervical, and colon cancer detection [4-6]. Primary care physicians play a key role in earlier diagnosis of cancer in symptomatic patients and in accessing treatment after the diagnosis [3]. As therapy improves, primary care physicians also will be increasingly expected to provide care for cancer survivors [7]. This article focuses on the role of primary care physicians in cancer screening. In particular, it provides an evidence-based approach to screening for five different cancers: breast, cervical, colorectal, ovarian, and prostate. These five cancers were chosen because they account for more than half of the total cancer deaths among men and women (Table 1) [2], and controversies exist for their screening strategies.