The growth of polypyrrole generated by electrochemical oxidation of the monomer was studied by two modeling approaches. The first is based on transition state calculations of successive coupling reactions to yield the polymer. The second evaluates the activation energy of coupling reactions by means of the frontier orbital model. The two methods predict a growth trend for polypyrrole in agreement with the structure inferred from spectroscopic investigations and provide a description of the electronic modifications induced by the growth of the highly conjugated structure. The first approach overestimates electrostatic interactions between the two reacting species, whereas the second neglects these interactions but exaggerates the importance of orbital interactions. Combining these two approaches allows separation of the electronic effects and leads to general rules for their evolution and their impact on the growth of polypyrrole. A theoretical framework capable of rationalizing solvent and counterion effects in electropolymerization is proposed. The first approach suggests a mechanism for defect formation which excludes reactions between a pyrrole radical cation and a nonterminal monomer unit of an oligomer chain. Oxidation of the successive oligomers at high doping levels is shown to be a key factor for the growth of long, regular polymer structures.