Pregnene-dione acetals and ketals

16,17-acetals and ketals of pregn-4-ene-3,20-diones of general formulae I and II. where R=H or acyl up to C12. P=H, alkyl, halo-alkyl, monocyclic cycloalkyl or -alkenyl; aryl or a heterocyclic group; or alkyl opt. substd. with monocyclic cycloalkyl or -alkenyl or aryl or a heterocyclic group. Q=as P excepting H. or CPQ=a monocyclic cycloalkyl or heterocyclic residue. Gestagenic agents, oral or parenteral; prevention of threatened abortion in animals. Instead of desoxycorticosterone for treatment in animals of renal insufficiency e.g uraemia, metabolic diseases with a disturbance of electrolyte equilibrium; and instead of cortisone as anti-inflammatory agent in allergies of eyes, skin and mucous membranes and in rhematic diseases. 7alpha, 16alpha, 17alpha,21-Tetra-HO-pregn-4-ene-3,20-dione-16,17-acetonide.