Certain substituted amines, alkylenediamines or polyamines, and derivatives of these, are suitable for use in preventing, inhibiting, or otherwise modifying crystalline gas hydrate formation. These inhibitors include compounds from any of the following groups. ##STR00001## The substituents R.sub.1-R.sub.5 may be hydrocarbyl groups or, in some cases, polyhydroxyalkyl groups or (CH.sub.2).sub.p--COO.sup.- in which p is either 1 or 2.