The thesis has two objectives. The first is to describe the vegetation in the State of Sabah. To this end all available knowledge has been examined and a classification scheme outlined based on ecological considerations. A more detailed classification of the dipterocarp forests into Types based on the relative abundance of big tree species is presented. The second objective is the development of management criteria to achieve satisfactory natural regeneration following logging in the dipterocarp forests and to enhance growth rates. An account is given of the dynamic Processes in the natural forest which lead to the replenishment of the species and this is followed by an examination of silvicultural treatments designed to influence the success of natural regeneration. Climber cutting and tree marking prior to felling are suggest`, ', as being useful in restricting the amount of damage done to the forest, particularly to soil and seedlings. After felling selective removal of unwanted species where these are likely to interfere with the growth of regeneration is advocated and a further intervention is recommended at 10-15 years 3tfter felling. Assessment techniques designed to measure desirability of treatment are discussed and preliminary results from yield plots are presented. Providing silvicultural treatments are undertaken it is estimated that second cuts in these forests may be taken at 60 years after felling. The stands will be essentially of the same suecies though refinement will have eliminated many of the AN less desirable timbers, and growth rates suggest that trees of the genus Shorea (section Rubroshorea) will be of most importance in the second growth stands.