The family Dipterocarpaceae may be estimated to comprise more than 500 Malaysian species. More than half of these occur on the island of Borneo, which for this reason can be considered to be the centre of development. The lowland forests up to about 700 m (2100 ft) altitude are characterised mainly by their richness in Dipterocarps. About 50 different species occur, for example, in the forests of Sandakan Bay, North Borneo, of which 20 are common emergent trees, whereas in the Apas-Balong area near Tawau about 60 different species were found. The timber export from North Borneo finds for more than 90 % its source in Dipterocarps. After preliminary studies by Symington, who visited the Colony during 1938, and by Wyatt-Smith (1952), this flora was more intensively studied by G. H. S. Wood, who was Forest Botanist in North Borneo from 1954—1957. Especially during the heavy flowering year 1955 he made extensive collections. His great ambition to become a monographer of the Borneon Dipterocarps could not be fulfilled owing to his tragic death in May 1957, [see B. E. Smythies, I960]. He left a manuscript about common Dipterocarps in North Borneo as well as unfinished descriptions of ten new species. An agreement has been reached between the Forest Botanist of Sarawak, Mr. P. S. Ashton, and myself to publish these new species in the course of our own studies of Borneo Dipterocarps [see Ashton, 1962]. Meanwhile it has been possible for me to unravel a number of taxonomic problems, to discover new species, and to make extensive new collections with which I began immediately after my arrival in North Borneo (May, 1959) and with which I was especially successful during the good flowering season of 1960. The revision can only make slow progress owing to the fact that it often takes a long time before flowers and fruits are collected from a new species. A number of hill Dipterocarps, for example, probably did not flower since 1955. During 1960 flowering was mainly restricted to the East-Coast. This paper is a precursor of a book on North Borneo Dipterocarps (Part I of the Foresters’ Flora on that region) which is at present in the press.