The catalytic hydration of 1,2-epoxy-3-butene was studied. The products of the reaction are 3-butenediol-1,2 (BD-1,2) and 2-butenediol- 1,4 (BD-1,4). It was shown that the formation of 2- butenediol- 1,4 proceeds predominantly in a polar solvent medium in the presence of the catalytic system "nickel iodide (bromide)-tetraethylammonium iodide" at a temperature of 80 degrees C. In the presence of inorganic acids, the main product is 3-butenediol-1,2.