The results of our experiments executed to obtain tobacco male sterile lines through interspecific hybridization are summarized. Ten wild species from the genus Nicotiana : N. excelsior ( exc ), N. amplexicaulis ( amp ), N. rustica ( rus ), Nicotiana glauca ( gla ), N. velutina ( vel ), N. benthamiana ( ben ), N. maritima ( mar ), N. paniculata ( pan ), N. longiflora ( lon ) and N. africana ( afr ) were used as cytoplasmic donors and N. tabacum , Cv. Harmanliiska Basma (HB) as a donor of the nucleus. Genetic effects of cytoplasmic-nuclear interaction of the studied species are discussed. Our results suggested that cytoplasmic male sterilty (CMS) was expressed when the cytoplasms of the above mentioned wild Nicotiana species were combined with the nucleus of N. tabacum . The 10 sources of CMS obtained in tobacco were characterized by altered flower phenotypes. Flowers are classified into types according the stamen, pistil and corolla modification. All these CMS sources were back-crossed to Oriental tobaccos, cvs. Tekne, Nevrokop B-12, Kroumovgrad 90 and Djebel 576, to develop corresponding CMS lines. The investigated cytoplasms produced compete male sterility in all those cultivars. The CMS lines preserved flower types, specific for every "sterile" cytoplasm. The extent of male organ modifications varied from apparently normal (but pollenless) stamens in CMS ( pan ), ( afr ), some plants of ( vel ) ( mar ) through different degrees of malformations (shriveled anther on shortened filaments ( lon ), pinnate-like anthers on filaments of normal length ( amp ), petal - ( ben ), pistil- or stigma-like structures (rus), (gla)) to lack of male reproductive organs in (exc) and in some plants of (vel), ( mar ), ( rus ) and ( gla ). Most of the above mentioned cytoplasms had normal female gametophyte and good seed productivity. Alterations of the pistils were observed in CMS ( rus ), ( exc ) and ( ben ) causing reduction of the seed set. Electrophoresis of seed proteins of the tobacco cultivars and their CMS lines also suggested that the nuclei of wild species was entirely displaced by the nucleus of N. tabacum . CMS lines with cytoplasms of N. velutina , N. maritima , N. paniculata , N. longiflora and N. amplexicaulis were selected as suitable for seed production in tobacco.