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The karyological and morphological variability of species from the genus Dysphania were studied. The results demonstrated that genus Dysphania is represented in Bulgaria by five species: Dysphania ambrosioides, D. multifida, D. botrys, D. schraderiana and D. pumilio. The first two species are tetraploids with chromosome number 2n = 32 for D. ambrosioides and 2n = 36 for D. multifida. The remaining three species are diploids with 2n = 18. The results from statistical analysis demonstrated that the main source of phenotype variation in the species is the interpopulation variation. The specific characters which allowed their recognition are the morphological characteristics of the perianth lobes, the upper leaves and the seeds. The distinction between D. multifida, D. ambrosioides and D. schraderiana is based on differences in the quantitative traits, while in D. botrys and D. pumilio qualitative traits are also important. The basic evolutionary mechanisms are polyploidy and diploidy. A tendency towards reduction in the size of generative organs and the number of perianth lobes was found.