Cytological studies were carried out on 6 species of Banisteriopsis and 4 species of Heteropterys (Malpighiaceae, Malpighioideae), collected in forest and cerrado areas of southeastern Brazil, and a cultivated one. No previous chromosome counts are known for 3 species of Banisteriopsis and 3 species of Heteroprerys. Chromosome numbers were obtained through mitotic (7 counts) and meiotic (5 counts) analysis. No meiotic abnormalities were encountered in the species studied, which presented high viable pollen rates. For the first time, karyomorphological characters were found for both genera, with a predominance of metacentric chromosomes. The chromosome number variation, based on x=5 and 10, with cases of polyploidy, and the similarity between the 2 related genera are discussed.