One hundred and fifty‐seven chromosome numbers of a range of taxa from both hemispheres are reported in the genusMentha.Plants of both wild and cultivated origin have been sampled, including hybrids, some of which have been synthesized from known parents. Some of the causes of the great taxonomic complexity of the group are discussed and the need for accurate and unambiguous identification of the plant material is stressed. There is a critical review of the chromosome numbers in relation to their taxonomy, with a discussion on probable basic numbers. The most useful areas of future research are indicate