Conditions required for the ethylene oxide sterilization of Bacillus subtilis var. niger spore strips wrapped in different types of packaging are reported. Both 100per thousand ethylene oxide and a Freon 12 - ethylene oxide mixture are studied. The packaging materials include 4-mil polyethylene, polyethylene/tyvek, paper, and paper/mylar. Both the packaging and the sterilization cycle play a role in effective sterilization using ethylene oxide.