Different start-up procedures have been applied on a crossflow microfiltration plant for the clarification of solutions from raw cane sugar. Compared to the abrupt start-up mode, a progressive setting-up of both transmembrane pressure and crossflow velocity allowed the permeate fluxes to increase significantly without any alteration of the clarifying effect. This result has been proved on three different lots of sugar under different operating conditions. (Résumé d'auteur)