Vertical Roller Mill (VRM) technology was developed more than four decades ago and has found applications mostly in cement grinding operations and in power plants for coal grinding. VRM technology has been well documented in literature to offer energy consumption reduction (from 15% to 30%) over conventional comminution units and circuits. These proven benefits of the technology have attracted the interest of the minerals industry. For this study, a prototype pilot-scale vertical roller mill with a ball race design was purpose-built and commissioned at Sepro Mineral Systems in Canada. Extensive bench-scale ore preparation and characterization tests, followed by pilot-scale VRM experimental programs, were conducted to determine the relationship between size reduction and energy requirement considering all critical operating variables. The effects of feed physical properties (top size, fines content), machine operating variables (applied compression pressure, table rotation speed, feed rate), and feed water content on product particle size and specific energy consumption were studied. Upon optimization of the feed and operating parameters, closed-circuit locked cycle tests were conducted to more accurately determine the energy consumption and ground product particle size distribution that simulates a production-scale comminution process flow sheet. Further work and recommendations were made based on a newly developed understanding of wet comminution using VRMs.