In Myrtaceae (Myrteae), the diploid chromosome number 2n = 2x = 22 is the most common, although variations of ploidy level occur, with some triploid ( 2n = 3x = 33) and tetraploid (2n = 4x = 44) records. Karyotype details in this group are scarce because the chromosomes are small (< 2 mu m). In this work, we carried out a karyotypic analysis of 15 species of Myrtaceae grouped in different subtribes and genera. Measurements of chromosome length (long arm, L; short arm, S) were taken and several karyotypic parameters were calculated for each species. The karyotypes in fleshy-fruited taxa (Myrteae) were more varied than in the other previously analysed dry-fruited group ( Eucalyptus, Eucalypteae), in which the chromosomes were exclusively metacentric. (c) 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 571-580.1554571580