At the Washington DC Pharmacogenomics in Drug Development and Regulatory Decision-Making: Workshop III - Three Years of Promise, Proposals and Progress on Optimizing the Benefit/Risk of Medicines (11-13 April 2005), one break-out session (Track 2) focused on co-development of therapeutic drug and diagnostic products. The Food and Drug Administration (FDA) released a draft concept paper shortly before the workshop was to convene. Track 2 was a forum for initial discussion of the content of the concept paper, and industry's initial reactions. After the workshop, formal commentaries on the co-development concept paper were submitted by several trade associations (e.g., Pharmaceutical Research and Manufacturers of America (PhRMA), Advanced Medical Technology Association (AdvaMed), American Association for Clinical Chemistry) and individual companies to FDA's Docket No. 2004N-0279. This paper includes a summary of the key features of the draft concept paper, the discussion in Track 2 of the April, 2005 meeting and highlights of the industry comments submitted to the FDA docket following the meeting.