An incomplete partial diallel cross was chosen to estimate quantitative genetic parameters in a breeding population of flue- cured tobacco. Two separated gene pools, an "East-population" originated from the former German Democratic Republic and a "West-population", were combined to produce F₁ hybrids. Five inbred lines of both populations occured in three crosses, resulting in 15 offsprings. Field trials including the hybrids and the parental lines were carried out in 1995 and 1996 at two locations, using a randomized complete block design with two replications. The characters yield, nicotine content, and tar content were assessed for calculating the quantitative genetic parameters. Variance components of general combining ability (gca), specific combining ability (sca) and their interaction with environments were calculated. Using these parameters, estimations for the heritability in a narrow sense were possible. The comparison between the performance of the parental lines and offsprings gave estimations of the extent of heterosis. The results indicate, that the genetic variation between the offsprings is mainly due to gca - variance and sca x environment - variance. Values of heritability are high for yield and nicotine content and medium for tar content. Heterosis for all characters is low in general; it is positive for yield and tar content, and negative for nicotine content.