Strains of the swine transmissive gastroenteritis (TGE) virus were isolated for the first time in Bulgaria in 1972. The dynamics was followed up of some strains' propagation in primary cell cultures of kidney tissue and subcultures of the thyroid of pigs. The intracellular virus reached highest titers at the 24--48th hour in the kidney cells, and at the 24--36th hour in the thyroid cells, while the extracellular virus was subjected to inactivation by the 2nd hour after infecting the cultures, by the 4--6th h its titer dropped up to 50 per cent of its initial value, and by the 24th h it was completely inactivated. The viability of the virus was tested after freeze-drying and after it had been stored at 4degreesC and--20degreesC. It was found that chloroform fully inactivates the virus at 4degreesC for 24 hours. The same results were obtained with the use of sodium desoxycholate. The strains isolated in this country form plaques, and with some strains the plaques are of a varying size. Halogenic desoxyuridines (IUDR, BUDR), as well as 8-azoridine do not suppress the multiplication of the tested TGE strains even in high concentrations. Inhibitory effect has 5-bromurazyl which in given concentrations affects the titer of the virus and the size of the plaques formed. Two Bulgarian and two reference strains have lowered their plaque-forming titer by 2 log after being treated with rifamycin-B or rifampicin.