This paper provides an overview of an ongoing study that aims at using a performance-based approach in the design of low clinker content concrete mixes. To replace the cement and hence clinker content, fly ash and three limestone fillers differing in particle size distribution were used. A review of a preliminary study that aimed at evaluating the effects of reducing the cement content on workability and compressive strength is provided. It was observed that a minimum paste content is required to attain suitable workability. The tests on strength indicated that suitable strength can be attained with low clinker contents if good mix design principles are applied.