Studies of the reproductive system and pollination syndrome of cultivated trees of Couroupita guianensis Aubl. are presented. The first report of the internal morphology of the stigma is included. In the stigmatic area two parts can be distinguished, one is hydrophobic and is composed of conspicuous collector hairs and the other is hydrophilic and is formed by the top of the transmission tissue; both parts have important functions fertilization. The flowers are odoriferous, nectarless and are visited by bees for their pollen. Osmophores are more evident the top of the filaments of the hood anthers. The pollen is morphologically and physiologically dimorphic. The fertility of the pollen was tested, in vivo and in vitro; under both conditions, only the staminal ring pollen germinated. The species is self-compatible. Pollen tubes begin to develop 45 minutes and arrive at the ovules 24 hours. The field observations and tests demonstrate that the species studied, although allogamous, is self-compatible. The Neotropical Lecythidaceae have been studied mainly with reference to the floral biology, focusing on the androecium. Monteiro-Scanavacca (1975), basing her studies on the vascular system of Lecythidaceae species, concluded that this family the application of the term androphore is erroneous, and defined the structure question as a body of fused stamens. Prance (1976) studied the pollination of six Amazonian species of Lecythidaceae from five genera, describing the complex androphore structure and the pollinators. Prance & Mori (1977) discussed androecium and fruit terminology of Lecythidaceae and commented on the similarity between the genera Lecythis and Couroupita. Mori et al. (1978) classified the New World Lecythidaceae three basic types according to floral structures: those with actinomorphic androecium being the most primitive (e.g., Gustavia), those with zygomorphic hood, flat (e.g., Couroupita) and coiled (e.g., Escheweilera), being more advanced. Mori & Orchard (1979) described the dimorphic morphology and physiology of the pollen of Lecythis pisonis Camb. and compared this pollen with that of Couroupita guianensis. The gynoecium, until now, has only been studied with reference to placentation. Monteiro-Scanavacca (1974), her studies of 12 species of Lecythidaceae, concluded that the basal portion of the ovary is multilocular with axillary placentation, becoming unilocular with parietal placentation the distal portion. In this paper the floral biology and reproductive system are discussed and the stigmatic region, style, and the tissues involved fertilization are defined. The