The family Malpighiaceae shows a great chromosomal number diversity, with polyploidy and disploidy between and within species. Cytological studies have played an important role in the taxonomy of Malpighiaceae. In the present work we studied twelve species and present the chromosome numbers and for seven of them karyomorphological characters and chromosomal ideograms. The chromosomes are predominantly small and metacentric. No meiotic abnormalities were found, and they presented a high viable pollen index. We analyzed the relationship between the taxonomic distribution of taxa and the distribution of chromosomal numbers in Malpighiaceae species. The sub-family Malpighioideae presents chromosome numbers based on x=5 and the subfamily Byrsonimoideae presents numbers based on x=6. The basic number x=5 for Malpighiaceae is a new proposal, supported by some counts for the genera Banisteriopsis, Heteropterys, Peixotoa and Tetrapterys.