Over half of the major papers published in the American Journal of Roentgenology (AJR) have five or more coauthors. This project was designed to evaluate the specific contributions of coauthors and the prevalence of undeserved authorship in major papers from institutions in the United States.Questionnaires were mailed to the first author of 275 major papers from institutions in the United States that were published in the AJR in 1992 and 1993. Questions focused on coauthors' contributions to research design, data collection, data analysis, and manuscript preparation, and on undeserving authorship.One hundred ninety-six (72%) of the surveys were returned. Ninety-nine percent of first authors, 75% of second authors, fewer than half of third authors, and one third of fourth authors and beyond were said to have contributed to at least three of the following: research design, data collection, data analysis, and manuscript preparation (p < .02). A strong correlation was indicated between authorship position and...