The deltaROxo-values, i.e., ratios of retention data for 3-oxo derivatives to those for the corresponding free sterols have been determined for fourteen 4-desmethylsterols, six 4-monomethylsterols and twenty-one 4,4-dimethylsterols on SE-30, OV-17, QF-1 and HiEFF-8B stationary phases. The QF-1 phase is found superior to the others in affording the values which are the most effective for differentiation between the three sterol groups. Within the same sterol group, the values for individual sterol members on any of the stationary phases differ to some extent due to minor variations in their skeletal structure. 4-Desmethyl-delta-5-sterols have strikingly large deltaROxo-values and are distinguishable definitely from other members of the 4-desmethylsterol group. The relative deltaROxo-values, i.e., ratios of deltaROxo-values of individual sterols to the deltaROxo-values of beta-sitosterol, also have been calculated from the deltaROxo-values of individual sterols.