The qualitative description of rock masses by means of classification systems and subsequent correlation to establish engineering quantities or design parameters has become one of the most challenging topics in rock engineering. Many rock mass classification systems have been proposed for rock masses with the consideration of a particular rock structure and/or specific purposes. Therefore, direct utilization of these systems, in their original form, for the characterization of complex rock mass conditions is not always possible. This is probably one of the reasons why rock engineers continue to develop new systems or modify and extend current ones. The recent tendency is to obtain rock mass properties from the utilization of properties of intact rock and rock classification indexes, which have some drawbacks. In this study, it is aimed to propose a new rock mass quality rating system designated as Rock Mass Quality Rating (RMQR). This new rock mass rating system is used to estimate the geomechanical properties of rock masses. In the first part of this paper, the input parameters of RMQR and their ratings are given and discussed. In the second part, the unified formula proposed by the first author is adopted for the new rock mass rating system for estimating the rock mass properties and compared with the results of the in situ tests carried out in Japan and those estimated from some empirical relationships developed by other investigators, and the outcomes of these studies are presented and discussed.