A simulation technique which is based on quantum mechanically generated probability distributions of alpha alpha, alpha beta and beta beta type linkages in polypyrroles is presented and applied for a statistical analysis of the growth process. The results show that the branching occur even at very short chains. The extent of the branching does not depend on the chain length and it is a slowly varying function of the temperature. At room temperatures, 20-25% deviations from the linearity is observed which is consistent with the experimental observations. (C) 1999 Elsevier Science S.A. All rights reserved.