The process for the continuous preparation of homopolymers or copolymers by free-impinging-jet micromixing of fluids formed (1) of monomer(s) and (2) of an initiator system consists in micromixing the said fluids (1) and (2) and in recovering the mixture of these fluids in the form of a resultant jet Jr, originating from the point of impingement (I), the micromixture being obtained by: a) forming at least one group of at least two jets Ja of the said identical or different fluids, these jets coinciding at a point of impingement (I), the jets Ja of the same group all being of identical geometry, their axes being arranged such that their projections on a plane perpendicular to the axis (A) of the resultant jet Jr are distributed angularly in a uniform manner and these axes being inclined relative to the said axis (A) by the same non-zero angle α of not more than 90°; b) simultaneously directing at the point of impingement (I) at least one jet Jb of a fluid which is different from at least one of the fluids of the said jets Ja for forming the resultant jet Jr, the axis of the jet(s) Jb being inclined relative to the axis of the resultant jet Jr by an angle β which is less than the angle α; and c) recovering the mixture of the fluids in the jets Ja and Jb in the form of the resultant jet Jr consisting of the homopolymers or copolymers.