For the detn. of natural unsatd. sterols, the dried, sieved soil sample is extd. continuously with hot alc. The extract is cooled, filtered, and the solvent removed by distn. The residue is refluxed 2 hrs. with amyl alc. containing aq. HCl. The solvent is evaporated, the residue taken up in anhydrous Na2SO4, and extracted continuously with light petroleum. The extract is made up to known vol., and the sterols detd. colorimetrically after purification via the digitonides. 56 soil samples of varying types were collected in the Brit. Isles, and their sterol content detd. Accumulation of sterols occurred under conditions of acidity, waterlogging and lack of aeration. In peat bogs a sterol content of 12.7 mg./kg. was found. The disappearance of soil sterols was demonstrated, and shown to result from microbiological activity.