In medical practice and research, sterilization of materials and equipment is frequently necessary to prevent infection. Steam pressure and other heat sterilization methods are usually satisfactory; however, a number of materials, certain instruments, and various types of apparatus are easily damaged by the high temperatures needed for steam or heat sterilization. This paper presents an evaluation of a new method of sterilization, which uses a nonflammable, nonexplosive mixture of ethylene oxide and halogenated hydrocarbons with low pressure characteristics in an automatically controlled sterilizer.