Two models of latent infection of continuous L23 cells caused by scrapie agent were developed using the method of cell cloning as well as DEAE-dextran and lidase preparations. The infectious activity was found only in cell homogenate L-C and L-506 (cells of clone L23 latently infected with the Compton and C-506 strains of the scrapie agent). A direct relationship between the infectious activity of the cell homogenate and the intensity of brain lesions revealed by morphological examinations of brain sections from infected mice was observed. The cytoplasm of L-C and L-506 cells became strongly vacuolated, piknosis of the nuclei and delay in the cell growth rate were noted. Cytogenetic studies established changes in the model class of the experimental cultures as well as the appearance of rearranged chromosomes.