This paper addresses the diachronic development of the periphrastic construction, beon/wesan + the participial ending -ende in Old English, into the progressive construction in Modern English. Even though there are two different hypotheses regarding the origins of the progressive – the beon/wesan + -ende construction and the locative construction with the verb be + the preposition on + the nominal ending –ung– it is suggested that both forms somehow merged giving way to the present day construction be + -ing. Some of the examples of the construction in Old English correspond to the present day usage of the progressive but not others and this is why it is suggested that the usage of the beon + -ende construction was still undeveloped. In Middle English, the ending –ende had different dialectal forms in different parts of Britain but finally the –ing form prevailed over the rest of the endings. New forms of the progressive developed in this period, leading finally to the grammaticalization1 of the construction in Modern English where it stopped being a stylistic variant and began to have a verbal status. Some of the new progressive forms developed in Modern English, such as the progressive passive, were forbidden by the grammarians. Nevertheless, the use of the latter form increased among literary people who used the construction in private letters to friends and as they started gaining prestige, this form was no longer forbidden. In this paper the semantic development of the construction will also be treated, showing the differences and the shift in meaning between Old English and Present Day English.