Non-ozone depleting sterilant compositions made of ethylene oxide and 1,1,1,2,3,3,3-heptafluoropropane. These compositions provide good sterilization characteristics, and are compatible with contemporary environmental concerns. One preferred aspect of the invention is a sterilant mixture comprising from about 20 mole percent to about 35 mole percent ethylene oxide and from about 65 mole percent to about 80 mole percent HFC-227 ea. Compositions comprising from about 25 mole percent to about 30 mole percent ethylene oxide and from about 70 mole percent to about 75 mole percent HFC-227 ea are preferred, with a composition comprising about 27 mole percent ethylene oxide and about 73 mole percent HFC-227 ea being most preferred.