The fundamental problem that the Grid research and development community is seeking to solve is how to coordinate distributed resources amongst a dynamic set of individuals and organisations in order to solve a common collaborative goal. The problem arises through the heterogeneity, distribution and sharing of the resources in different virtual organisations. Interoperability is a main issue for applications to function with the Grid. This paper proposes a matchmaking framework for service discovery in Grid environments based on three selection stages which are context, semantic and registry selection. It provides a better service discovery process by using semantic descriptions stored in ontologies which specify both the Grid services and the application knowledge. The framework permits Grid applications to specify the criteria a service request is matched with and enables interoperability for the matchmaking process. A proof of concept is done with a prototype implementation, and an enhancement of the matchmaking process is achieved with a similarity metric which allows quantifying the quality of a match. A qualitative and quantitative evaluation of the prototype system is given with an analysis and performance measurements to quantify the scalability of the prototype.