The aim of this paper is to assess the suitability of a significant number of carbonate rocks from the Aitoloakarnania province (Western Greece) for their use as road construction aggregates, in terms of their content in swelling clay minerals. The study focuses on Cretaceous limestones from the Olonos-Pindos zone. Detailed petrographic analysis and the sand equivalent and methylene blue tests are carried out, in order to estimate the quantity of swelling clay minerals in aggregate particles. Special emphasis is given on correlating the results of the sand equivalent and methylene blue tests, as well as on the relationships between these engineering parameters and the petrographic data. The results are evaluated in accordance with the Greek and International suitability Standards for road construction aggregates. Although the results of the sand equivalent test indicate the suitability of the studied samples, the results of the methylene blue test imply that they are not suitable for use in all applications of road construction. Hence, it is proved that the methylene blue test is of fundamental importance for the determination of the lithotypes which are suitable for use as road aggregates in various applications.