In spite of the importance of mycorrhizal associations in the facilitation of mineral absorption and improvement of productivity in plantations, mycorrhizal associations have hardly been involved in management programs of tropical rain forests. A project is being carried out within the Tropenbos Cameroon Programme (TCP) to study the mycorrhizal associations in the tropical rain forest of south Cameroon. One hundred timber species of various importance and local Gnetum species were selected. Three sites were chosen at low (50 - 350 m), mid (350 - 500 m) and high (500 - 800 m) elevations. In each site, two experimental plots were set in primary forest. A selective inventory was carried out. Microscopic root observation allowed to determine the mycorrhizal status of selected species. Seventy species formed uniquely vesicular arbuscular mycorrhizae (VAM) ; thirty timbers and the three Gnetum species formed ectomycorrhizae (ECM). Few dual mycorrhizal associations were observed. VAM associations prevailed in most vegetation stands. However, numerous ectomycorrhizal lianas of Gnetum existed in fallow of Chromolaena odorata. On the other hand, ECM timber species occurred in clusters in primary forest stands at the three sites. Such a floristic distribution may serve as a sound basis for the setting of conservation areas and implies particular silvicultural treatments.