Conformational properties of 1-alkylhexahydroazocin-5-ones (I; R = Me, Et, Me2CH, Me3C) were studied by He(I) photoelectron, 13C NMR, and IR spectroscopy as well as MM2 and MNDO calcns. The mol. structure of I (R = Me3C) was detd. crystallog. The eight-membered ring in I has a boat-chair conformation with the functional groups occupying positions with the shortest possible transannular distance (.apprx.270 pm).