The three-dimensional orientation of the hydroxyl group in stereoisomeric 1,2,7-trimethyl- and 1,2-dimethyl-7-tert-butyldecahydro-4-quinolols and their 4-ethynyl-substituted derivatives was established by IR spectroscopy. The possibility of a twist conformation of the heteroring in 1,2,7-trimethyl- and 1,2-dimethyl-7-tert-butyldecahydro-4-quinolols with an equatorial hydroxyl group is shown.