Abstract: In this paper, karyotypes from fifteen populations in thirteen species of Euphorbia (Euphorbiaceae) from China were investigated. The results were as follows: 2n=2x=22=20m (2SAT)+2sm for Euphorbia humifusa (Wangjiang, Sichuan); 2n=2x=22=18m+4sm for E. humifusa (Hongqicun, Beijing); 2n=4x=40=40m for E. thymifolia; 2n=4x=40=36m+4sm for E. maculata; 2n=8x=56=40m+8sm+8st for E. marginata; 2n=4x=40=32m+8sm for E. milii; 2n=6x=60=6m+36sm+12st+6t for E. neriifolia; 2n=6x=60=24m+24sm+12st for E. antiquorum; 2n=4x=28=24m(3SAT)+4sm for E. pulcherrima; 2n=4x=28=16m+12sm for E. cyathophora; 2n=4x=28=28m for E. dentata; 2n=2x=20=12m+8sm for E. lathyris; 2n=6x= 42=36m+6sm for E. helioscopia; 2n=2x=20=14m+6sm for E. esula (Chenjiagou, Beijing); 2n=4x=40=32m+8sm for E. esula (Yingtaogou, Beijing). The karyotypes of two species, E. thymifolia and E. maculata, and the tetraploidy karyotype of E. esula were reported for the first time.

Key words: Euphorbia, Euphorbiaceae, karyotype, polyploidy, cytotaxonomy