Morphological characters and chromosome number of ten cultivars and five species of aromatic Pelargonium, as well as ornamental cultivars, were compared. The oil cultivars are very alike morphologically and they are supposed to be clones of P x asperum. They have irregular meiosis with high frequency of univalents and are male sterile; their chromosome number is 2n=77. Some of the species (P. graveolens from Italy, P. odoratissimum, P. tomentosuni and P. grossularioides) agree with previous descriptions, but others, as P. graveolens from Argentina and P. radula from Italy, were probably introduced with a wrong classification. Their chromosome number were counted and compared to previous determinations with excelent agreement. No data was found concerning P. grossularioides; the present chromosome counting seems to be the first. The ornamental cultivars studied here belong to the species P. zonale; some are diploid, others tetraploid; in the diploid cultivars mixoploidy is frequent. As chromosome number is concerned, three basic numbers were established; x=8 for P. odoratissimum, x = 9 for P. grossularioides cv. cocoanut, P. graveolens from Italy and P. zonale (ornamental cultivars), and x=11 for P. graveolens from Argentina, P. tomentosuni, P. radens and P. x asperum (aromatic cultivars).