This document provides a summary of the 2016 annual review of leading healthcare information systems (HIS) vendors ranked by revenue. It discusses the long history of such vendor reviews dating back to 1980. Definitions of what constitutes an HIS vendor are provided, excluding large firms only involved in hardware, consulting, or specialty systems. Revenue figures for 2015 are presented for the top HIS vendors along with analysis of changes from 2014 revenue and notable trends. The review highlights the continued leadership of Cerner, as well as growth of athenaHealth and its new entry into the hospital HIS market.