A discussion of Silurian stratigraphical classification is followed by detailed comments upon the correlation of Llandovery, Wenlock, Ludlow, and post-Ludlow pre-Gedinnian rocks throughout the British Isles. A main correlation chart shows selected successions in Wales and the Welsh Borderland, North-West England, and Scotland. Subsidiary charts relate respectively to the Silurian inliers south-east of the main Welsh outcrops and to those of the Midland Valley of Scotland. A separate chart is provided for all the Irish Silurian. The concealed Silurian rocks of Eastern and Southern England are considered relatively briefly, as are the enigmatic records from Cornwall. Finally a chart and short commentary serve to correlate the Silurian successions of Bohemia, Thuringia, Podolia, Estonia and Gotland with the standard employed here for the British Isles. There is an extensive bibliography.