This study presents the results of an author co-citation analysis of the interdisciplinary field of medical informatics.An author co-citation analysis was conducted for the years 1994 to 1998, using the fifty most-cited American College of Medical Informatics fellows as an author population. Co-citation data were calculated for every author pair, and multivariate analyses were performed to ultimately show the relationships among all authors. A multidimensional map was created, wherein each author is represented as a point, and the proximity of these points reflects the relationships of authors as perceived by multiple citers.The results from this analysis provide one perspective of the field of medical informatics and are used to suggest future research directions to address issues related to better understanding of communication and social networks in the field to inform better provision of information services.