Greek has always been assumed to possess a verbal system organized on the basis of aspect, with tense playing only a secondary part, and to have retained this state of affairs throughout its history. This article claims that it has changed substantially, moving from the expression of oppositions of Aktionsart (states – telic activities – atelic activities) to the expression of oppositions of grammatical aspect (perfective – imperfective) and tense (past – non past and later past – present – future). The current system is claimed to display an almost perfect balance between tense and aspect.