The brown pud disease caused by phytophthora leads to serious loss of production in cocoa growing areas. The priority area of the flight was the selection of cocoa-trees with low sensitivity to this disease. The search for cocoa-trees with total resistance remained vain in spite of several attempts made. This suggests to the existence of partial resistance which is probably very polygenic. The transmission of characters of resistance to this disease seems to be mainly additive. Nevertheless, ignorance about the species of phytophthora which causes this disease has for a long time delayed the progress made by genetic control because each species has special epidemiological characteristic which require specific methods of control. The scope of losses in a given country therefore depends on the species found there and climatic conditions. Since 1980, four main species of phytophthora which cause cocoa disease have been characterized : P. megakarya (Africa), P. palmivora (all cocoa zones), P. capsici Acacoa (America) and P. citrophthora at Brazil. Within the framework of this study, we will only talk about the results obtained with the two most aggressive ones (P. megakarya and P. palmivora). The large collection of material isolated from these two diseases causing agents found at CIRAD Montpellier (about 900 stems), from all cocoa growing areas enabled us to carry out the following work with the objectives being: to characterize the level of aggressiveness of stems representative of P. megakarya and P. palmivora (isolated in 1994-95). (Texte intégral)