Abstract: Alkaline earth metal alkylates having a spherical particle habit are prepared by dissolving an alkaline earth metal alkylate in a solvent, adding a second solvent which dissolves the alkaline earth metal alkylate only with difficulty or does not dissolve it at all, but which is homogeneously miscible with the solution of the alkaline earth metal alkylate in the first solvent, removing the first solvent and then removing the second solvent. The particle size can be controlled by means of the shear gradient during the precipitation or by the use of emulsion stabilizers. Emulsion stabilization leads to particles in the size range 0.5 to 20 .mu.m with a particularly narrow particle size distribution. Catalysts for polyolefin synthesis can be prepared on the basis of magnesium alkylates prepared by the process according to the invention. The polymer is advantageous with respect to particle habit and particle size distribution, compared with the prior art.