Spontaneous cacao trees ( Theobroma cacao L.) found in south-eastern French Guiana form a particular genetic group, the “Guiana” group, which could be used in cacao breeding. Since 1987, CIRAD* has set itself the objective of collecting and characterizing those cacao trees, carrying out agronomic and sensory assessments, and studying the ir diversity. The main results acquired are presented. Four surveys took place from 1987 to 201 2 in the upper reaches of the Oyapok and Tanpok rivers. The plant material collected, from 226 moth er-trees, has been planted in a collection at CIRAD 's Sinnamary station, as open-pollinated progenies or clones. The trees are observed individually for ten years for various agronomic descriptors: juvenile growth, adult vigour, early yielding, yields, “cropping efficiency”, percentage of rotten pods and average pod weight. Various morphological, biochemical and molecular de scriptors have been used to study the diversity of the “Guiana” group. Resistance to black pod rot caused by stramenopiles of the genus Phytophthora (P. palmivora and P. capsici) was assessed in early tests and many resistant clo nes have been identified. Sensory studies have revealed a cocoa f lavour that is statistically better than that of the industrial reference (“West African Amelonado”). As this germplasm seems very promising in cacao breeding, it is therefore important to continue sur veys in French Guiana (some zones have yet to be surveyed) and maybe in the Guiana Shield, and to as sess all clones for their performance in relation to other pests and diseases.