The kinetic features of the alkylation reaction of butandiol-1,4 with allyl chloride in the two-phase "liquid-liquid" systems composed of the organic phase and diol and "liquid-liquid-solid" formed in the presence of an excess solid alkali were studied. The concentration effect of the phase-transfer agent, the alkali, the substrate, and the alkylating agent on the product yield was examined. A mechanism of the alkylation reaction of symmetric diols involving the interface was proposed on the basis of the results.