The relevance of petroleum coke activity during the plastic stage in cocarbonization with a low-volatile bituminous coal was assessed by establishing differences in lowering of Gieseler maximum fluidity of the blend (bituminous coal and petroleum coke) and in metallurgical coke quality. Differences in fluidity of the blend were well correlated with parameters used in petroleum coke characterization such as hydrogen donor ability, the volatile matter released between 400 and 500 degrees C, and the ratio of methyl and methylene groups in aromatic clusters, The metallurgical cokes were produced in a laboratory oven from blends of petroleum coke-bituminous coal and, then, characterized in terms of abrasion strength and reactivity to CO2. There is a clear relation between the chemical activity of petroleum coke in cocarbonization systems with coal and improvements in metallurgical coke quality. The ability of petroleum coke to interact with coal during the plastic stage contributes to good bonding between components as evidenced by the quantitative study of interfaces by optical microscopy.