This corpus-based study examines the use of support verb constructions in Old English and Old Irish. It determines in how far these constructions can be seen as a means to offer semantic specification of existing verbal expressions. The study further investigates whether support verb constructions may be employed to create periphrastic verbal expressions to denote concepts for which no simple verb exists in the language at that stage. This latter situation may particularly arise as a consequence of contact with new cultural concepts. The approach of the study is both qualitative and quantitative. It compares the use of the Old English constructions to corresponding Old Irish structures as well as to other language varieties, especially Present Day English, which has a considerably more analytic morphological structure than either of the two medieval languages.