SummarySoil from a field under long‐term grass was treated with 0.02msodium periodate for various periods up to 1176 h, followed by 0.1dsodium tetraborate for 6 h. This destroyed an increasing proportion of microaggregates>45 μm and carbohydrate. After periodate treatment for 6 h about 70% of the soil sugars remained in the residue as measured by reducing sugar content and about 67% as individual sugars measured by gas‐liquid chromatography. After 48 h the reducing sugar content was about 45%. An inverse linear relationship was established between the proportion by weight of microaggregates>45 μm and residual carbohydrate. The residual carbohydrate showed an enrichment in sugars commonly found in plant materials; glucose, arabinose and xylose, suggesting that the microbial carbohydrate had been preferentially destroyed. When the concentration of the periodate was increased to 0.05mthe residue contained about 50% of the original carbohydrate after 6 h treatment, and 25% after 48 h and an additional increase of about 10% in the proportion by weight of particles in the<45 μm range.These results throw doubt on the validity of assumptions made in a number of studies about the limited extent to which soil polysaccharide is involved in aggre