Among the many viruses that infect tobacco, members of the potyvirus group, potato virus Y (PVY), tobacco etch virus (TEV), and tobacco vein mottle virus (TVMV), are widely distributed and cause significant economic crop losses in many countries. Numerous strains of these viruses have been described, they are insect transmitted, and host resistance represents an important component of disease control. Sources of host potyvirus resistance investigated in our laboratory include burley cultivar TN 86, which possesses the major recessive gene from Virgin A Mutante (VAM), cigar binder cultivar Havana 307 (HA 307), and burley cultivars SOTA 6505 and S-3. HA 307, SOTA 6505, and S-3 were hybridized with TN 86 and near isogenic lines of TN86 which are virus susceptible. All of the resistant cultivars appear to possess a single gene that is allelic to the recessive gene conferring resistance in TN 86. NC 602, a gametoclonal variant flue-cured breeding line, possesses a single gene which acts in an additive fashion, and provides resistance to two necrotic American strains of PVY, but it is susceptible to TEV. The NC 602 gene is not allelic to the VAM gene, and genotypes have been produced wich combine the two genetic systems for PVY resistance. NC 152 is a flue-cured doubled haploid homozygous for a chromosome from Nicotiana africana which possesses a gene(s) for TEV and PVY resistance. This gene(s) acts in a partially dominant mode. Attempts are being made to combine all three resistance sources into a single genotype. Resistance to other virus diseases will also be discussed.