In the course of a systematic study into the recognition of prokaryotic organic matter in sediments, a sample from a very recent, lacustrine sediment (Lake Vechten, The Netherlands) was analysed by a method applying sequential extractions and hydrolyses. Three different modes of occurrence of lipids (free, OH −-labile and H +-labile) are distinguished. Most lipid moeities occur in different modes. The free compounds are primarily even, long chain fatty acids and alcohols (>C 20) and sterols, the latter showing low values of the Δ 5-stenol/5 α(H)-stanol ratio. The OH −-labile components are mainly derived from the plant macromolecules cutin and suberin. The extract containing exclusively H +-labile lipids shows abundant β-hydroxy fatty acids which occurred probably amide-bound in the original organic matter. These H +-labile β-hydroxy fatty acids are specific for bacteria and their distribution is considered a fingerprint of the prokaryotic community. The lipids in the sediment are dominated by markers of higher plant material. Since the input of higher plant material is calculated to be of minor importance, the organic geochemical record does not reflect the relative contributions to the carbon budget of the lake. This indicates that the biodegradability of incoming organic matter and the mode of occurrence of the lipids in it are major factors determining the composition of lipids in sediments.