OBJECTIVES: To systematically review reports that queried abstract authors about reasons for not subsequently publishing abstract results as full-length articles. STUDY DESIGN AND SETTING: Systematic review of MEDLINE, EMBASE, The Cochrane Library, ISI Web of Science, and study bibliographies for empirical studies in which investigators examined subsequent full publication of results presented at a biomedical conference and reasons for nonpublication. RESULTS: The mean full publication rate was 55.9% [95% confidence interval (CI): 54.8%, 56.9%] for 24 of 27 eligible reports providing this information and 73.0% (95% CI: 71.2%, 74.7%) for seven reports of abstracts describing clinical trials. Twenty-four studies itemized 1,831 reasons for nonpublication, and six itemized 428 reasons considered the most important reason. "Lack of time" was the most frequently reported reason [weighted average = 30.2% (95% CI: 27.9%, 32.4%)] and the most important reason [weighted average = 38.4% (95% CI: 33.7%, 43.2%)]. Other commonly stated reasons were "lack of time and/or resources," "publication not an aim," "low priority," "incomplete study," and "trouble with co-authors." CONCLUSIONS: Across medical specialties, the main reasons for not subsequently publishing an abstract in full lie with factors related to the abstract author rather than with journals.