Nonpublication of research results threatens the integrity of clinical research, but the extent of nonpublication and factors associated with publication remain poorly documented. We sought to examine rates of publication or presentation of research findings from multicenter clinical trials and determine what factors are associated with dissemination of results.

We conducted a follow-up study of 217 prospective, multicenter clinical trials of treatment approved in 1998 by the institutional review board of a large academic medical center, of which 197 had enrolled participants and were not known to be ongoing. Follow-up included searches of the literature and the Internet and telephone and e-mail inquiries to investigators and research sponsors. The main outcome measures were manuscript publication or other presentation of research results.

Results of 110 (56%) out of 197 multicenter clinical trials have been published in the peer-reviewed literature. Results of 87 (44%) studies have not been published, and results of 52 (26%) studies have not been disseminated in any form. The rate of dissemination of trial results was highest for studies that were phase 3 (81%), lowest risk (86%), and investigational (76%). The dissemination rate was lowest for studies that were supported by internal funds (50%). However, none of these associations were statistically significant.

Results of almost half of the multicenter clinical trials conducted in part at a large academic medical center have never been published. Mechanisms to ensure public dissemination of clinical trial results are needed.