Diseases involving abnormal glycoconjugation are frequently diagnosed by enzymic methods of varying complexity (Table 1) and/or by analysis of abnormally excreted carbohydrate-containing material. Gas-liquid chromatography-mass spectrometry (GC-MS) has been used to detect specific compounds known to be excreted in some glycogen storage diseases and muscular dystrophies (Lennartson et at., 1976) and in mannosidosis (Lundblad et al., 1975). This method has now been extended for use as a general screening method for the detection of low molecular weight carbohydrate-containing compounds.A number of oligosaccharides are present in normal human urine and include lactose, maltose, isomaltose, fucosyl-a-( 1-2)-glucose, xylosyl-a-( 1-3)-glucose, fucosyl-~-(1-O)-inositol, a glucose-containing tetrasaccharide and a series of disaccharides to pentasaccharides, the presence of which depends on ABO blood group, secretor status and diet (Lundblad et al., 1973). The amounts of these compounds excreted are usually quite low ( < 20 rag/24 h). In certain diseases additional compounds are excreted in much larger amounts, for example in mannosidosis a mannose-containing trisaccharide and tetrasaccharide are excreted in quantities up to 470 and 60 mg/24 h respectively (Lundblad et al., 1975; Norddn et al., 1974) and a glucose-containing tetrasaccharide is excreted in amounts approaching 90 mg/24 h in certain glycogen storage diseases (Lennartson et al., 1976).The overall picture therefore is of a complex mixture of low molecular weight carbohydrate-containing material which can show considerable non-pathological variation, but in at least some pathological states this pattern is overshadowed by great excesses of specific compounds or series of related compounds.The basic procedure developed to analyse urinary oligosaccharides involves desalting 20 ml of ultrafiltered urine through Dowex 50 (H +) and AG-3 (OH-) resins, fbltowed by reduction of the oligosaccharides with sodium borodeuteride and methylation (Lundblad et al., 1975). The methylated and reduced oligosaccharides are then separated by gas-liquid chromatography (GLC ; Perkin-Elmer 3920 : capillary column, 25 m x 0.25 mm, wall-coated with SE-30; temperature programme 230 °C/30 min, 230 °C 330 °C at 4 °C/rain, 330 °C/30 min) and identified by mass spectrometry (Varian MAT 311A, 70 eV, 1 mA, ion source 120°C) linked to a Spectrosystem 100 computer. The resulting chromatogram contains a large number of peaks grouped in the monosaccharide and disaccharide regions, but the trisaccharide to pentasaccharide region is usually dominated by a few compounds as shown for a normal blood group B secretor individual in Figure 1. The major component is the blood group B trisaccharide (Lundblad et aI., 1973). Also shown is the glucosecontaining tetrasae.charide (Glq). By comparison, the same region of the chromatogram is shown for urine from a mannosidosis patient in Figure 2. The only significant peaks in this case are two of the mannosecontaining oligosaccharides which cannot be degraded by...