Abstract: A process for the preparation of stable aqueous polycarbodiimide dispersions, to be used as crosslinking agent, which are free of organic solvents is described. Sid process is characterized in: reacting a polyisocyanate in the presence of a carbodiimide catalyst to form a polycarbodiimide, terminating and/or chain extending the polycarbodiimide chain by the addition of formation dispersion of the resulting compound in water, wherein pH is adjusted to a value between 9 and 14 by the addition of a base and/or a buffer to the water used for the dispersion and/or to the obtained aqueous dispersion. According to the present process said terminating or chain extending with the compound containing a hydrophylic group and one or more amine functions may also occur during or after the dispersion of the polycarboiimide in water. The preferred pH of the polycarbodiimide dispersions is between 11 and 13.