Dietary fibres (DF) - their chemical composition and structure, physico-chemical properties, and physiological effects - comprise and area of increasing scientific interest. Progress in this research is, however, rendered somewhat difficult by the disagreement concerning demarcation of the DF concept. In the present study, a physiological based method of analysis for determination of total DF (TDF) corresponding to the sum of insoluble DF (IDF) and soluble DF (SDF) have been used as an initial step in studies of DF from different rape seed varieties and biorefined fractions of double low rape seed compared to DF from peas. A comprehensive characterization of DF from rape seed and peas have been performed, with determination of the neutral monosaccharide composition by different techniques as a first step. The yield of sugars, especially glucose, was found highly dependent on the procedure used for hydrolysis of the polysaccharides. The composition of the polysaccharide fractions also differed according to the type of plant material. This diversity was further emphasised by results from sequential extraction and separation of isolated DF leading to fractionation of DF into four groups: pectins, hemicelluloses, celluloses, and lignins. UV-VIS-spectroscopy of extracts from these groups provided useful information concerning the presence of material of non-carbohydrate origin. The hemicellulose fractions from peas and especially rape seed were shown to have the highest content of proteins and phenolics, possibly being present as strongly adsorbed or covalently bound components. The protein part of the DF fractions was further investigated by biochemical methods of analyses including affinity chromatography, electrophoresis as SDS IEF, and the presence of myrosinases was demonstrated in DF from rape seed. Peas also comprised DF associated proteins, although the level was considerable lower than found in rape seed DF. High performance capillary electrophoresis methods for determination of phenolics have been developed in order to provide an efficient tool for characterization of the phenolic DF components. Application of the above mentioned methods to studies of DF and fractions of DF have demonstrated the presence of appreciable amounts of protein and various types of low molecular weight compounds, especially phenolics, associated to DF.