The energy differences between stereoisomers and the ring inversion potential surfaces of decalin (1) and various oxadecalins (2, 3), dioxadecalins (4-7), trioxadecalins (8, 9) and tetraoxadecalins (10, 11) were interrogated following the generally accepted scheme of a stepwise conformational six-ring inversion process and using molecular mechanics techniques (MM3 and MM3-GE, i.e. MM3 reparametrized for treatment of the ''gauche effect''). The results were compared with some available experimental data and were also used to probe the validity of a recently elaborated protocol for ring-fragment analysis of oxygen-containing bicyclic systems in terms of their interannular fragment components: C-C-C-C, C-C-C-O, C-C-O-C, C-O-C-O-C and O-C-C-O, the latter two with their corresponding stereoelectronic effects, namely, the ''anomeric effect'' and the ''gauche effect'', respectively.