Thermal decomposition of petroleum vacuum residue (XVR), polypropylene (PP), Bakelite (BL), Samla coal (SC), bagasse (BG), Calotropis procera (CL, a petrocrop), and their mixtures with petroleum residue was studied in a batch reactor under isothermal conditions at atmospheric conditions. The product distribution patterns have been determined. Kinetics of their thermal decomposition were also studied in order to compare the kinetics of cracking of individual materials with that of the mixture. Activation energy as well as rate constants have been calculated for the materials as well as their mixtures. Cocracking of a mixture of XVR, PP, and CL was found to show synergism of activation energy. The detailed results obtained are reported.