Extended calculations of soot formation in the pyrolysis of a number of hydrocarbons varying in chemical structure have been performed. The computer code for soot formation was based on the "polyyne model", which uses the "acetylene pathway" to soot particles. The model treats soot formation as a process of chemical condensation (polymerization) of supersaturated polyyne vapor (C2nH2, n = 2, 3,....). This process results in polymeric globules as primary soot particles. The computer code is based on a detailed description of both gas-phase and heterogeneous reactions, soot particle nucleation, their surface growth and coalescence. The principal parameters for soot formation, such as induction time, soot particle number density, and soot volume fraction over a wide temperature range have been calculated. There is good quantitative agreement between these calculations and available: experimental measurements for methane, acetylene, ethylene, diacetylene, benzene, and naphthalene as fuel. (C) 2000 by The Combustion Institute.