The application of high-pressure roll mills (HPRM) for industrial comminution has been growing, particularly because of its energy efficiency. Many aspects of HPRM comminution have not been fully characterized because the performance of the machine is affected by numerous parameters that still need to be investigated and optimized. The present paper is concerned with the effect of feed moisture on HPRM performance. The comminution of minus 8-mesh dolomite feed at several different moisture levels was conducted with a laboratory HPRM to delineate the effect of feed moisture on product characteristics, specific energy consumption, and such mill operating parameters as applied load, roll gap and roll speed. The results showed definite effects of moisture on these parameters and the product size distribution, most likely because of lubrication of the particles in the compacting bed as they pass through the roll gap. (C) 2007 Published by Elsevier B.V.