The relatively recent introduction of new Burley and Virginia type tobaccos has changed the phytosanitary situation of tobacco growing and in particular the relative importance role of virus diseases. They were unknown and until recently considered as causing slight damage. During the three last years samples were collected from different tobacco production areas in France in order to determine the major viruses to be plegded to this culture, and to define a few caracteristics for some of them. Most of the samples were infected by PVY and CMV, either alone or in complex in plants. TRSV and AMV were found only sporadically, the plants infected by the latter one were often localized in the plots near alfalfa fields. TMV, TSWV and TEV were never found. CMV isolates studied by direct DAS-ELISA test belonged to two thermoresistant strain types (DTL) and to known thermosusceptible ones. These strains cause great damage, especially in Burley tobacco and a great variety of symptoms in the three important tobacco types grown. The numerous PVY isolates collected were graded according to their responses on flue-cured tobacco varieties susceptible or resistant to Meloidogyne incognita and PVY. They were also compared to American reference strains. Both mosaic (MM) and necrotic (NN and VAM-B) strains were discovered. MN strains with necrotic potentialities on NC 95 comparable to those of the American reference strain were never detected. The isolates VAM-B were at different degrees able to circumvent resistance provided by the recessive gene va and by the VR gene issued from in vitro androgenesis, and were necrotic with regard to Burley 21 genotype. These strains seem to possess potentialities allowing them to attack most of the dark and bright resistant tobacco varieties known. Their frequency seems to be low and their competitivity should be appreciated.