The instant invention relates to a process for the preparation of stabilizers for polymers, especially for polyamides, by condensation of isophthalic acic dichloride (IPC) with sterically hindered amines of the type tetraalkylpiperidine. By using organic solvents or mixtures of organic solvents with water and by an optimized combination of temperature and pressure the yield is much higher than by using water alone. The organic load of the waste water could be significantly reduced.