AbstractThe composition of lipids from severalEnchytraeus(Annelida, Oligochaeta) andTisbe(Arthropoda, Crustacea) populations or species, respectively, has been investigated using chromatographic and spectrometric methods. Triglycerides and polar components were found to be the predominant components. In both genera, the fatty acid moiety of the triglycerides consisted mainly of saturated and unsaturated C14‐, C16‐ and C18‐compounds; particularly, inTisbepopulations additionally branched constituents were present. Predominantly fatty acids inTisbepopulations were C16‐compounds whereas C14‐compounds were major constituents inEnchytraeusindicating a differently oriented synthetase activity in these groups. The analysis of the fatty acid profiles and the phospholipid patterns revealed distinct groups within theEnchytraeuspopulations which can be discriminated by a different balance of ß‐oxidation and desaturase systems. These findings are discussed in context with the fatty acid metabolism in these organisms considering the results obtained with other methods and evaluating the applicability of lipid analysis in these organisms for chemosystematic in