The compounds are ethylene derivatives which are inhibitors of histamine activity, in particular, inhibitors of H-2 histamine receptors. A compound of this invention is 1-nitro-2-[2-((4-methyl-5-imidazolyl)methylthio)ethylamino]-2-[2-((3-chlor o-2-pyridyl)methylthio)ethylamino]ethylene.