A process is described for the preparation of propylene glycol and ethylene glycol from formaldehyde, the first step involving conversion of the formaldehyde into a mixture of polyhydroxyl compounds in a conventional manner in an alkaline medium by self-condensation and the second step involving catalytic hydrogenolysis of this mixture with a hydrogen consumption of at least 0.5 mol of hydrogen per mol of formaldehyde employed for forming the polyhydroxyl compounds.