The UDFT method has been successfully applied to study the thermal conversion of Z-1,3-hexadien-5-yne, 1 to benzene, 4. UB3LYP calculations give excellent agreement with available experimental energy values. A four-step mechanism is predicted. The results are compared with the previous studies. It has been shown that an applicational error caused shortcoming of the previously suggested three-step mechanism, which is corrected by inclusion of the global minimum, 1a, of the starting compound in the suggested mechanism.