This study investigates the various forms of m(i)entre in the Alfonsine corpus in order to determine when it is used as an adverb and when it is used as a semi-suffix, with an eye to determining the possible reasons for these different usages. In the corpus of Alfonsine texts available in the Old Spanish Textual Archive, we have found 21 instances of m(i)entre; in 11 instances it is used as an adverb and in 10 instances it is used as a semisuffix.