A new method of determination of the lateral order of cellulose fibres is proposed．1t is based on the measurement of the density of the fibre by the loss of weight method in a series of sodium hydroxide solutions of increasing concentration from zero to 2N．Due to the gradual penetration of the swelling agents into the fibre texture，the density values change step by step，the increments of density being plotted against sodium hvdroxide concentrations to yield the lateral order distribution curve．The slight error resulting from the partial solubility of the fibre in sodium hydroxide of higher concen-trations is corrected．The method is direct，simple，quick，of high power of resolution and good reproducibility．It seems to possess many advantages over current methods of tudying lateral order which in turn is the most essential dement in the characteriza-tion of the supermolecular structure of cellulose fibres．