The high resolution photoelectron spectra for the following iodine-containing molecules have been measured: iodomethane, 1-iodoethane, 1-iodopropane, 1-iodobutane, 1-iodopentane, 1-iodohexane, 2-methyl-1-iodopropane, 3-methyl-1-iodobutane, 2-iodopropane, iodocyclopentane, iodocyclohexane, 2-methyl-2-iodopropane, trifluoroiodomethane, 2,2,2-trifluoro-1-iodoethane, pentafluoroiodoethane, 3,3,3,2,2,1,1-heptafluoro-1-iodopropane, iodobenzene, pentafluoroiodobenzene, vinyl iodide, allyl iodide. The spectra are discussed in terms of extended Hückel (EH) molecular orbital calculations and of the qualitative changes upon variation of the alkyl group.