Work has been done in Poland on the cultivation of varieties resistant to Lycopersicum Virus 3 since the Sixties. In the first stage of the work we looked at wild species to find sources of genetic resistance. The species Nicotiana alata proved resistant. In 1970 we undertook some hybridization, using a wild form _ Nicotiana alata _ as the maternal component and the cultivated tobacco _ Nicotiana tabacum as the paternal. At the same time, a test method to find this pathogen in plants examined under greenhouse conditions was developed. Generation F1 of the hybrid was found to be unfruitful. We were able to overcome this infertility by treating the young plants in the seedbed phase with 0,5% colchicine solution during 24 hours. We undertook retrograde hybridization with Nicotiana tabacum 4 times. Selfpollination took place only in B3. During the whole breeding phase positive selection was undertaken, choosing plants in good health on the basis of an artificial infect ion with TSWV-virus in the greenhouse. It can be stated that the resistance against TSWV is hereditary in successive generations and that it is a monogenic dominant factor for the hypersensitive type. Some lines of this hybrid were cultivated in the field during 1982 and 1983 under natural conditions, allowing for the possibility of infection by TSWV-virus, which is transmitted by Thrips tabaci Lind. The lines were found to be 100% resistant also under natural infection conditions. During the selection of the hybrid some male infertile lines, resistant against TSWV, were also obtained. Those forms, that were pollinated with pollen from the variety Nicotiana tabacum, demonstrated a morphology approximate to that of commercial tobacco and full resistance against TSWV.