Over 50 medical and advocacy organizations have jointly authored an open letter to the U.S. Administration calling for clear guidance to regulate the implementation of a statute protecting patient access to clinical trials. At present, only 6% of patients with severe chronic illness and fewer than 5% of cancer patients participate in clinical trials. This low participation rate hampers the progress of research necessary to develop much-needed new treatments. To promote and protect patient participation in clinical trials, the Patient Protection and Affordable Care Act ('Obamacare') contains a provision that mandates coverage of routine medical costs for people who participate in approved clinical trials. However, the details of implementing this provision are left up to the individual states, which may lead to uneven and unpredictable coverage. The letter points to a 2010 study showing that patients have been denied coverage of their clinical trial costs, even in states that already require such coverage. The letter signatories therefore call for federal guidelines for implementation to be issued before the provision goes into effect on January 1, 2014.