During 1952 and 1953, Mr. R. F. Wood, one of the Commission’s forest officers, who had been awarded a Travelling Fellowship by the Nuffield Foundation, visited the forests of British Columbia and the neighbouring territories, to carry out field studies. This region is the home of several trees, such as the Sitka spruce and the Douglas fir, which have become important in British silviculture, but few comparative studies of the two environments, in relation to tree growth, had hitherto been made. The purpose of this Bulletin is to examine and discuss the growth of these timber trees, as observed in North-West America, with particular reference to its implications for forestry practice in the British Isles.