Background: Industry supported randomized controlled trials (RCTs) and meta-analyses are more likely to yield conclusions that favor sponsors interests, even controlling for study quality. Reporting guidelines require authors of RCTs and meta-analyses to report study funding and potential conflicts of interest (COI), but there is no formal requirement to report funding and potential COI of included RCTs in meta-analyses. Objective: To investigate the extent to which meta-analyses transparently report industry funding and author financial ties of included RCTs. Methods: A sample of meta-analyses of pharmacological treatments published January-September 2009 that investigated at least one drug patented in the US was selected. Up to 3 meta-analyses, beginning with the most recently published, were selected from general medicine journals with impact factor =10. In addition 3 meta-analyses were sampled from each of 5 specialty medicine areas with the highest 2008 global therapeutic sales (oncology, cardiology, respiratory medicine, endocrinology, gastroenterology) and from the most recent Cochrane Library issue. For specialty areas, the top impact-factor journal was searched, followed by the second highest-rated journal until 3 eligible meta-analyses were identified. Results: Only 2 of 29 selected meta-analyses reported funding sources of included trials and none reported author financial ties or author affiliations. Based on preliminary data from 90% of included RCTs (460/510) in the 29 meta-analyses, 53% (245/460) had industry funding, author employment, or other author financial ties: 43% (199/460) of included RCTs reported study funding from pharmaceutical sponsors, 25% (113/460) reported at least one author employed by industry, and 17% (76/460) reported other author financial ties. In 6 meta-analyses, 100% of included trials had at least one link to industry, but none reported included RCT funding or potential COI. Conclusion: Information on funding and potential author COI often disappears when data from RCTs are incorporated into meta-analyses.