Karyological information on Iberian Ophrys species is very limited. This paper provides the haploid and diploid chromosom numbers of 11 taxa of sect. Pseudophrys and sect. Ophrys, both of which are well represented in the Iberian Peninsula, and two taxa from Tunisia. The first data on chromosome numbers for O. vasconica (2n = 72, 74), O. ficalhoana (2n = 36), O. picta (2n = 36), O. sphegifera (n = 18, 2n = 36, 38) and O. passionis (2n = 36) are also presented, confirming the stability of the chromosome number in Ophrys. In addition, populations of the group O. omegaifera (O. dyris and O. vasconica), together with tetraploidy, pentaploidy and the existence of aneuploid phenomena, are reported for the first time in Iberia. The basic diploid number is always 2n = 36. The karyotypes of several species were analysed. Evolutionary trends in Ophrys chromosomes are discussed. Taxonomic and phytogeographical details are provided on several species or groups of species from Iberia. (C) 2003 The Linnean Society of London.