The study of the breeding system of Anadenanthera falcata, Vochysia tucanorum and Xylopia aromatica is the main purpose of this work. The field work was carried out from November, 1985 to November, 1987. The three species showed a breeding system preferably xenogamic. It was observed in Vochysia tucanorum a small fruit production by autogamy, what could be considered as an alternative strategy. A high degree of genetic self-incompatibility was demonstrated in Anadenanthera falcata and Xylopia aromatica which associated to its dicogamy patterns favoured cross-polination (xenogamy).