ABSTRACT: Most rock mass classification schemes fall short in meeting the demands of increasingly complex contractual conditions for today's infrastructure projects, where cost and risk control plays a major role. The concept for rock mass characterisation proposed in this paper systematically aims towards: a) the definition of typical rock mass behaviour and b) the recognition and description of geotechnical risks. The product is the definition of rock mass types (RMTs) that supply the information required for tunnel design as well as for ground-related contractual issues.