The results of polymerase chain reaction and of DNA sequencing of the Adel2 mutant variant of adenovirus serotype 5, passaged 10 times and capable of selectively infecting and lysing the p53-deficient human tumor cells, are indicative of a high stability of its genotype and of the phenotypic properties acquired by it in successive passage on 293 cells. The absence of admixtures of wild-type adenovirus was clearly shown in the cultivation and passage processes. It was revealed in an experimental analysis of virus-productive properties of the studied continuous cell culture 293 by using the method of multilayer cultivation, that the maximal Adel2 yield is obtained at the 50% cytopathic effect. Virus doses, that are effective for cell-culture contamination, are within a range of 100-10 TCPE50 per cell. In order to spare the viral material, the infecting dose of 10 TCPE50 per cell was chosen to infect a cell monolayer.