The systematic measurement of sample plots in stands of growing timber provides the data for the compilation of yield tables and other estimates of increment which are essential to the economic management of woodlands. In order that such measurements shall be strictly comparable, both as between one sample plot and another, and within the same plot as measured on different occasions, a precise method must always be followed. This bulletin sets out in detail the procedure that has been developed by the Forestry Commission’s research officers since such measurements were begun in Britain, under the Board of Agriculture, forty-five years ago. Though intended primarily for the staff engaged on such work, it is believed that it contains much information of value to all who are concerned with the raising and accurate measurement of timber trees, both at home and abroad.