In the last years, the development of ontology-based applications has increased considerably, mainly related to the Semantic Web. Users currently looking for ontologies in order to incorporate them into their systems, just use their experience and intuition. This makes it difficult for them to justify their choices. Mainly, this is due to the lack of methods that help the user to determine which are the most appropriate ontologies for the new system. To solve this deficiency, the present chapter proposes a method, ONTOMETRIC, which allows the users to measure the suitability of existing ontologies, regarding the requirements of their systems. ONTOMETRIC, based in the analytic hierarchy process, can be used to select the mostappropriate ontology among various alternatives. This chapter describes the main techniques and activities to apply the method.