The aim of this paper is to report the results of a study of Murcian speech in order to measure the increasing diffusion of standard Castilian features from northern Peninsular Spanish over Murcian Spanish, a traditionally non-standard region. Following the methodology used in similar studies and a real-time approach, we measured the level of standardization of people interviewed in radio broadcasts in the last 26 years. A detailed analysis correlating linguistic variables with social variables and time intervals allowed us to compare the sociolinguistic behavior of the different social groups in terms of standardization (adoption of Castilian Spanish features) or non-standardization (maintenance of local Murcian features) and their tendencies in diachronic terms.