During the reaction of 1-butene catalyzed by W03-Si02, a small amounts of volatile compounds were injected into the reactor. The products were analyzed by gas chromatography, and the effects of addition of the compounds on the disproportionation and isomerization of 1-butene were evaluated. Hydrogen chloride, chloroform, carbon tetrachloride, certain brominated cornpounds, butylamine, and isobutylamine promote the disproportionation and inhibit the isomerization. Water, ethanol, diethyl ether, ethylene glycol, 1-fluorohexane, and diethyl sulfide promote the isomerization and inhibit the disproportionation. Carboxylic acids, their derivatives, nitro- methane, piperidine, and certain halogenated compounds inhibit the disproportionation and isomerization. Compounds, capable of promoting the above both reactions, were not found. The compounds, capable of promoting the disproportionation by pulse addition, were added continuously to the reactor; the continuous addition mostly showed similar results as above, but some of them showed different results. From these experimental results, it is suggested that the catalyst of an unstable state, formed by the interaction of W03-SiO2 catalyst and a halogenated compound, is very active for the disproportionation but the halogenated compound itself rather interfere with the reaction.