Nepeta L. is one of the most important genera of the Lamiaceae family, which widely distributed all over the word. The members of this genus are use of traditional and modern medicine. Nepeta species growth naturally in various parts of Iran and recent years the number of its species is increasing. In the study, morphological characteristics of twenty four populations of seventeen Nepeta taxa were used for infra-generic classifications, because there were many discussions about infra-generic classification of this genus. For this, forty qualitative as well as quantitative morphological features of both vegetative and reproductive organs were examined. Data were analyses with MVSP and SPSS softwares. ANOVA test showed significant variations for all the studied quantitative traits, with the exception of flower number per cycle. Furthermore, most of qualitative characters such as basal and floral leaf shape and petal color differed between taxa. PCA-biplot and CA joint plot showed that some morphological characters had taxonomic value and were useful in identifications of species. In many cases, clustering of species in the UPGMA tree, PCA and PCO plots did not confirm species placements in groups/ sections according to modern classifications. Furthermore, populations of same species did not cluster closely. It seems that ecological conditions had strong effect on different features of this study and high infra-specific variations were found among the studied species.
