The two cytopatogenic strains of horse herpes virus—1 (KH9F and Vivac) reproduce successfully in primary cellular cultures of swine kidney, as well as in constant cellular lines of swine kidney—SPEV, of rabbit kidney—RK -13 and the line of calf trachea. When compared, RK—13 turned out to be the most sensitive line with quick and maximum accumulation of virus. However the rest of the lines prepared can also be used in the following order: SPEV, calf trachea, primary kidney, and PK—15. The peak moment of the reproduction of virions is the 18 Th. hour and not, as it has hither to been accepted, the 24th hour. After that, between the 24th and 48th hour a complete falling off of the cellular monolayer occurs due to the virus leaving the nucleus and its penetration into the cytoplasm of the contaminated cells.