Two-month old piglets previously inoculated with different dilutions of the Lapinized Chinese (LC) strain of Hog Cholera Virus (HCV), adapted in a minipig kidney (MPK) cell line, resisted challenge infection with virulent HCV. All the animals remained healthy and the challenge virus was never recovered from any of them. In contrast, the pigs which served as controls for the challenging virus underwent the clinically lethal form of the disease and HCV was consistently recovered from their tissues.