A process for the production of polymers by poly-condensation or ring-opening polymerisation with the addition of either (a) a 1-component catalyst consisting of amino- and/or hydroxy-carboxylic acid, or (b) a 2-component catalyst consisting of (b1) dicarboxylic acid or a functional derivative thereof and (b2) diamine with no OH groups, diol, mono-hydroxy-amine, or a mixture of such diamines and diols.
