Because diagenesis of organic matter in post-glacial lacustrine sediments is minimal, organic compounds characteristic of the source organisms should be present in the sediment profile and may constitute indicators of changing environmental conditions during the last 12,000 years. To verify this hypothesis, analysis of six sections from the complete postglacial sediment profile of Cam Loch (Sutherland, Scotland) is reported. The composition of the sterol and n-alkanoic acid fractions is indicative of the relative input from terrestrial and aquatic biota, while the alkane fraction is related to the terrestrial source material and amount of microbial activity. The abundance of branched/cyclic alkanoic and n-alkenoic acids is influenced by the trophic status of the lake. Additional compound classes associated with terrestrial input are methyl n-alkyl ketones, n-alkanols, α,ω-dicarboxylic acids and ω-hydroxyacids. It is shown that these observations provide a record of changes in source material and trophic status complementary to and consistent with the record deduced from the morphological residues and inorganic chemistry of an adjacent site.