Objectives: To determine the relationship between the quality of articles and whether they were published in a supplement or in the parent journal.

Data sources and study selection: All randomized control trials of drug therapies in adults published in the American Journal of Cardiology, the American Journal of Medicine and the American Heart Journal from January 1990 and obtained in November 1992 by means of a MEDLINE search. A total of 318 abstracts appeared to meet our inclusion criteria, and these articles were obtained and reviewed in further detail. An additional 76 were excluded.

Data extraction: Three reviewers who were "blinded" and thus unaware of supplement status independently assessed the quality of each of the remaining 242 articles according to a standard quality scoring system.

Data synthesis: Overall, 67 (27.7%) of the articles were published in journal supplements. Article quality scores ranged from 4.2% to 87.5%, with a mean (+/- SD) score of 37.2% +/- 13.1%. Quality scores were lower in articles published in journal supplements than in those published in the parent journal (t[240] = 2.61, P = .01). The mean quality score for articles published in journal supplements was 33.6% +/- 12.8% compared with a score of 38.5% +/- 13.1% for articles published in the parent journal. Supplement articles included in their final analysis a smaller proportion of the patients initially randomized (t[75] = 2.8, P = .007).

Conclusion: Our findings suggest that randomized control trials published in journal supplements are generally of inferior quality compared with articles published in the parent journal. The review process surrounding the publication of journal supplements should be consistent with that of the parent journal.