Publicly traded contract research organizations (CROs) have been playing a disappearing act. During the past eight years, 13 contract clinical research service providers that were formerly public companies have moved into the private equity markets. Much to the confusion and surprise of many professionals in the clinical research enterprise, some of the largest market-leading CROs--including Quintiles, PRA International, and PharmaNet--have transitioned out of the public markets. The recent acquisition of Kendle International and the potential acquisition of PPD by privately held INC Research and private equity firm the Carlyle Group, respectively, continue this trend. Poor global economic conditions for drug developers and unforgiving and intensifying investment community scrutiny have made the public markets less attractive to CROs. But there is more to it. Behind the veil afforded by the private markets, CROs have far greater latitude to not only complete transactions that complement their capacity and expertise and permit a founder to exit, but also to pursue novel leading strategies that may ultimately redefine integrated drug development services in the future.