Abstract: A method for a single step sterilization of a ready-pack, such as a blister pack, in an autoclave is described. The ready pack includes a container, such as a syringe, filled with a substance. The environment in the autoclave, that is, the temperature, the heating period and, preferably, the pressure is controlled to sterilize simultaneously the ready-pack and its contents by circulating steam in the autoclave. The steam penetrates into the blister pack through a steam-permeable base. The temperature is maintained between about 120.degree. C. to 130.degree. C. for about 15-20 minutes.