After the solvent extraction of the unbound lipids contained in a Recent lacustrine sediment, the remaining bound monocarboxylic acids were released by applying multi-step hydrolysis procedures. The relative and absolute abundances of these acids in the various hydrolysates differ greatly, thus clearly demonstrating that reliable comparisons of the fatty acid contents and distributions in various sediments require identical extraction methods. Systematic investigations show that after mild hydrolysis using either 5% KOH - methanol or 2 N HCl, the sediment still retains a large part of its fatty acids, which can be extracted after either hydrolysis in 6 N HCl or thermal treatment in 2 N KOH. The hydrolysis in HCl is much more efficient, but produces artifacts. The amounts of tightly bound fatty acids released by such treatments are important with respect to the total acid content and most of these acids are of bacterial origin. Their incomplete extraction would thus lead to greatly underestimating the microbial contribution to the sedimentary fatty acids.