Abstract: The syntheses of 5-pregnen-3β-ol-20-one esters and 3,5-cyclo-pregnan-6β-ol-20-one derivatives are described. Animal tests (inflammatory granuloma pouch) gave the following results: the salicylate and benzoate of 5-pregnen-3β-ol-20-one possess significant anti-inflammatory action, equivalent to that of Antiflamisonum The other esters of 5-pregnen-3β-ol-20-one (chloroacetete, trichloroacetate, furan-2'-carboxylate, p-toluenesulfonate, phthalate)and 3,5-cyclo-pregnan-6β-ol-20-one were found to be somewhat more active than Antiflamisonum.In order to interpret quantitatively the relationship between the lipophilic properties and anti-inflammatory activities, partition coefficients of pregnenolone derivatives were calculated from the hydrophobic fragmental constants. It was noticed that when logP0 the anti-inflammatory activities of all compounds except those of 3-methoxy-5-pregnen-20-one and 3β-chloro-5-pregnen-20-one, increased correspondingly with the increase of their partition coefficients. It was found that the correlations of anti-inflammatory activities and partition coefficients of this series were of parabolic dependence.