A method for precipitation of finely divided solid particles comprising a) Dissolving a compound C in a fluid A to provide a solution A; b) Thermostatization of said solution A to a temperature ranging between -50.degree.0 C. and 200.degree. C.; c) Adding a fluid B to said solution A until a pressure P is obtained, characterized in that said fluid B at a pressure P is miscible with said solution A and acts as a co-solvent to form a solution AB; d) Adding an inert gas to solution AB so as to maintain the pressure P; and e) Reducing the pressure of said solution AB so as to produce the precipitation of said compound C, and wherein the method permits particles of average size less than 20 .mu.m, with a narrow distribution ranging between 1 and 100 .mu.m, from a solution, and not a mix, that contains the compound C precipitated.