Purpose - This paper aims to examine the role of network effects (defined as increased utility for users of a technology that occurs when adoption increases among other users) in the adoption of electronic medical records (EMR) systems. EMR systems, which have experienced slow adoption rates, promise to improve the efficiency of the healthcare system by facilitating information exchange among physicians caring for the same patients. Design/methodology/approach - Survey responses from physicians are used to test several hypotheses. The authors are interested in how market level EMR adoption was related to physician adoption intentions. The authors also test the "strong ties" notion of network effects by examining whether EMR adoption among generalists, and specialist physicians, had differing influences on adoption intentions in a given market. Findings - Support for network effects is found; each one unit increase in market-level EMR adoption is associated with a significant increase in overall physician adoption intention in that market. Secondary analyses suggest adoption of EMRs by specialists is significantly predictive of generalists' adoption intentions in a given market. However, as predicted, EMR among generalists does not influence other generalists' intentions; nor does EMR adoption by a specialists influence other specialists' intentions. Research implications - Network effects play a role in the EMR adoption among physicians. Decision-makers wanting to influence adoption should target defined market segments in an effort to build a critical mass of adoption then move to adjacent segments once network effects take hold. Originality/value - This paper applies network effects theory to help explain the suboptimal adoption rates of an important healthcare technology. © Emerald Group Publishing Limited.