At high temperatures, in anionic polymerization, depolymerization and autocyclization reactions cannot be ignored and the molecular weight distribution (MWD) results based on irreversible polymerization give erroneous results. In this article, we have developed a semianalytical solution for the MWD of the polymer for a general complex mechanism. We then show that the various rate constants can be directly determined from the experimental data on MWD. After evaluating these, it is possible to model the anionic polymerization more rationally, as we have demonstrated using the experimental data from the literature.