Written and archaeological sources from the Mediterranean region have been exhaustively searched for evidence of historical volcanism before the year A.D. 630. Volcanic eruptions are identified here by two methods: direct observations, which give information about Mediterranean volcanoes, and indirect, atmospheric observations, which give at least the dates of very large explosive eruptions that occurred somewhere in the northern hemisphere. Seven or more very large explosive eruptions have been detected by these methods. Direct observations indicate great eruptions of Thera (fifteenth century B.C.), Etna (44 B.C.), and Vesuvius (217 B.C., A.D. 79, A.D. 472). Indirect observations imply great eruptions of northern hemisphere volcanoes in the years 217 B.C., 44 B.C., A.D. 472, A.D. 536, and A.D. 626. Some of the correlations with known Mediterranean eruptions may be accidental. It is found that atmospheric veiling and cooling were quite marked for about a year after the eruptions of 44 B.C., A.D. 472, A.D. 536, and A.D. 626 (relevant data are lacking for the other eruptions). If the A.D. 536 eruption was a very distant one (Rabaul, New Britain?), it may have been the most explosive in recorded history. There is independent evidence of the sizes of the eruptions that took place in these years: at least five of them coincide with the strongest acidity signals in Greeland ice for this period. In the case of the smaller eruptions, reliable (though necessarily incomplete) chronologies are presented for Etna, Vesuvius, and the other active Mediterranean volcanoes. Full documentation from the original sources is provided throughout.