The compounds 4,5-ethylenedithio-1,3-dithiole- 2-thione, 4,5-(methyl) ethylenedithio-1,3-dithiole- 2-thione and 4,5 (dimethyl) ethylenedithio-1,3- dithiole-2-thione were prepared by reaction of 1,3-dithiole-2,4,5-trithione with ethylene, propylene and trans-2-butene, respectively. The preparative and spectroscopic data are identical with those obtained from the corresponding authentic samples.