The aim of the present investigation is to study the genetic control of Erysiphe cichoracearum resistance of PMR Burley 21 cultivar, coming from N. tabacum. At the same time the inheritance of some quantitative characters was studied, that influence the tobacco yield. Investigations were carried out in 1988-1990 at the Institute of Genetics _ Bas. Sofia, Bulgaria. Erysiphe cichoracearum resistance was estimated by artificial inoculation with Erysiphe cichoracearum D.C. population, using TERNOVSKI's method. The resistance was studied in cotyledon phase by the method of DELON and SCHILTZ (1978) in planting phase and on the field. The number of genes, controlling the resistance was defined, using Square chi method. The resistance in F1 of hybrids, obtained by crosses of PMR Burley 21 with susceptible cultivars was recessively inherited. The genetic analysis in F2 indicates that the resistance to Erysiphe cichoracearum for the same cultivar is controlled by two recessive genes, this confirm the WAN's results (1962). The plant height and number of leaves in the hybrids studied is dominantly and overdominantly inherited.