Diploid chromosome numbers are presented for 31 species of Passiflora in subg. Plec- tostemma (sect. Cieca, Pseudodysosmia, Xerogona, Decaloba), Passiflora, Distephana, Tacsonia, and a few species of uncertain alliance. All but one of the counts are of neotropical taxa and the majority are the first reported for each. We remove P. sanguinolenta from subg. Psilanthus and transfer it to subg. Plectostemma, sect. Xerogona, based on morphological and karyotypic evidence. There are two basic numbers that are widespread in Passiflora: the relatively symmetrical and large karyotype of x = 9, which is reported for subg. Passiflora, Distephana, and Tacsonia; and the more asymmetrical and smaller karyotype of x = 6, counted here for subg. Plectostemma.