The solid-state polymerization of functional derivatives of 2,4-hexadiin-1,6-diol caused by light or by heat was investigated. A qualitative survey demonstrates that the presence of groups capable of hydrogen-bonding are one of the most important factors for solid-state reactivity of conjugated triple-bonds. Compounds which do not form hydrogen-bonds were unreactive in most cases. Urethanes were the most reactive class of derivatives, 2,4-hexadiin-1,6-diol-bis-phenylurethane giving the best results. The relation and the reactivity of several modifications of this compound are described. Heating of one modification of 2,4-hexadiin-1,6-diol-bis-phenylurethane at temperatures between 70 and 120°C yielded in a topotactic reaction highly crystalline fibres of a coppercoloured polymer. Time-conversion studies were made and the activation energy of the polymerization determined to 19 kcal/mole. The mechanism of polymer-formation is discussed. It is highly probable that poly-1,4-bis-phenylcarbamoyloxymethyl-trans-butatrien, a polymer with three cumulated double-bonds per repeating-unit, is formed by a 1,4-addition reaction.