As much as eighteen million acres in England and Wales consists of grassland, and considerable attention has been paid in recent years to its improvement. The need for authoritative information on this important subject led to the publication of Bulletin No. 3, “The Improvement of Grassland”, by the Ministry of Agriculture and Fisheries, a fourth and revised edition of which has been issued (Is. net). The revision of the text has largely been carried out by Prof. J. A. Hanley (Armstrong College, Newcastleupon-Tyne) who has taken the opportunity of incorporating in the present issue the deductions drawn from the work done under the Ministry's ‘Grassland Campaign’, and also to include a section on the comparatively new system of rotational or ‘managed’ grazing. The sections on the renovation of worn-out grassland and seed-so wing remain substantially as written by Prof. R. G. Stapledon, of the Plant Breeding Station, Aberystwyth.