This article reviews the chemistry of substituted polyacetylenes developed by our research group, more specifically, development of polymerization catalyst, synthesis of new polymers, elucidation of their structure, investigation of their properties, and development of their functions. The main features are as follows: a number of catalysts based on group 5, 6, and 9 transition metals (Nb, Ta, Mo, W, and Rh) have been developed, which include living polymerization catalysts. By using these catalysts, many new substituted polyacetylenes have been synthesized, whose molecular weights are very high (MW = 10(4)-10(6)). Most of the polymers are soluble in many common solvents and stable enough in the air unlike polyacetylene. Some of these polymers exhibit interesting functions including high gas permeability and photoelectronic properties. (c) 2006 Wiley Petiodicals, Inc.