Background: The core functions of Cochrane Fields include searching specialized sources for relevant studies, and compiling specialized databases of trials. In 2007, the Cochrane Complementary and Alternative Medicine (CAM) Field began improving the quality and comprehensiveness of the CAM Field specialized register. Objective: To describe the processes and outcomes involved in developing the CAM Field specialized register of trials. Methods: We began by improving the quality of the current CAM specialized register. CAM Field staff then instituted regularly updated searches for additional trials in PubMed and CENTRAL, using the PubMed complementary medicine search strategy, and incorporated newly identified randomized controlled trials (RCTs) into the register. The CAM Field also subcontracted with the Canadian Chalmers Centre for Systematic Reviews to search electronic databases for CAM trials and identify trials not present in MEDLINE or EMBASE, and with the Beijing University of Chinese Medicine to search Chinese electronic databases and identify and translate Chinese-language trials in Traditional Chinese Medicine. Results: The CAM Field specialized register initially contained 4,569 RCT records. PubMed searches retrieved an additional 9,580 RCT records. 2,504 trials identified by the Chalmers Centre and 1,778 trials identified by the Beijing University of Chinese Medicine were submitted to the CAM Field in 2007 and 2008. The addition of these trials, together with results of updated searches of CENTRAL and PubMed, culminated in over 20,000 CAM specialized register records submitted for Issue 2, 2009 of CENTRAL. An unexpected challenge in building the register was that the PubMed complementary medicine search strategy retrieved many non-CAM records from PubMed and CENTRAL, and there were time costs in removing non-CAM records from search retrievals. Conclusions: Using the PubMed complementary medicine search strategy to search for all RCTs on all CAM topics will retrieve many non-relevant trials. Possible strategies for dealing with this situation are being explored. Collaboration with international groups was extremely helpful in identifying trials from sources other than MEDLINE or EMBASE and in languages other than English.