SUMMARYB horizons from a set of 23 Scottish soils were examined by Py/MS multivariate analysis. These soils comprised phaeozems, cambisols, podzols and gleysols.The principal components analysis of 52 mass ion intensities partitioned the set of soils successfully according to morphological classes Bw, Bg and Bs, and established characteristic differences of organic composition between them. Reconstructed factor spectra for the factors effecting this partition showed distinct homologous groups of products to be responsible. These were principally pyrroles, alkenes and aromatic hydrocarbons of low molecular mass. Possible organic origins of these are discussed and related to the organic patterns found in the A horizons.The Bh (humus B) horizons of podzols gave pyrolysates richer in polysaccharide and lignin products than those of other B horizons, suggesting a less decomposed organic matter.