This report presents a general overview of non-stoichiometric step-growth polymerizations (polycondensations). Three kinds of non-stoichiometric polycondensations are defined and discussed for a(2) + b(2) monomer combinations. Depending on the kinetic scenario and on the experimental conditions, the excess of one monomer either strongly reduces or strongly enhances the average degree of polymerization (DP) relative to a stoichiometric polycondensation under identical conditions. As a result, telechelic oligomers or extremely high molar mass polymers (DPs > 1000) may be formed. Stoichiometric imbalance has in all cases the consequence that cyclization is largely suppressed in early stages of a polycondensation. Finally, non- stoichiometric a(2) + b(n) polycondensations are discussed.