A convenient synthesis of 1,2-didehydroaldosterone acetate, from 11β-hydroxypregna-1,4-dien-3-one, is described. Photolysis of the 11-nitrite of the latter compound gives only the desired attack at C-18. The resulting 18-oxime is cyclised to the nitrone, and the oxidation level of the latter is conveniently used for the introduction of a 21-acetoxy-group. Similar experiments with 11β-hydroxypregna-1,4,6-trien-3-one afford 1,2,6,7-tetradehydroaldosterone acetate. Selective hydrogenation of 1,2-didehydro- or of 1,2,6,7-tetradehydroaldosterone acetate gives aldosterone acetate in unlabelled or labelled (tritium) form. An interesting cleavage of steroid 18,20-nitrones with chromic acid (Jones reagent) has been discovered and shown to regenerate the masked aldehyde function of aldosterone-type compounds. A systematic study of the photolysis of 11β-nitrites has defined the best solvent and other conditions for this reaction.