The crystal structures of 13-ethyl-gona-1(10)-ene-11alpha,17beta-diacetate (3b) and 13-ethyl-10alpha-gona-4-ene-11alpha,17beta-diacetate (5b), two steroidal monoenes obtained as minor products from the reduction, then acetylation, of the aromatic A ring of 13-ethyl-3-ethoxy-gona-1,3,5(10)-triene-11alpha,17beta-diol (1), were determined by X-ray diffraction. The conformations of the rings A, B, C, and D and the unusual stereochemistry at C-10 of the 10alpha-gona-4-ene (5b) are discussed.