Three independent syntheses of 18-methylideneprogesterone, the first representative of a new group of biologically highly active steroidal compounds, are described. In the first approach 3-acetoxy-20-oxo-5-pregnen-18-carbonitril ( 2 ) is transformed into the final product by a reaction sequence involving the Cope degradation of the N -oxide 6 of the corresponding tertiary aminomethyl derivative. The Wittig reaction 3,3,20,20-Bis(äthylendioxy)-5-pregnen-18-al ( 11 ) represents the crucial step in the second synthesis. In the last procedure the 18-methylidene-20-oxo grouping is generated by fragmentation of an 18,21-bridged 1,3-diol system ( 19 ). The two former methods are very versatile and generally applicable for the synthesis of other analogues.