Azeotropic and azeotrope-like compositions of methyl iodide and at least one fluorocarbon or hydrofluorocarbon such as 1,1,1,3,3-pentafluoropropane (HFC-245fa). The compositions are present as a gas, at temperatures of about 30° C. or below. The inventive compositions serve as a non-ozone-depleting gaseous fumigant which is useful in a variety of applications, in place of methyl bromide. These compositions serve as a drop-in replacement for gaseous methyl bromide, providing the benefits of a methyl iodide fumigant while also utilizing existing methyl bromide equipment.