Nitrogen adsorption isotherms have been determined on commercial samples of the disperse dye, C.I. Disperse Red 54. The samples contain considerable proportions of dispersing agent. Low BET surface areas (0.3-0.5 m2g-1) were obtained. For some samples, the nitrogen isotherms are reversible or exhibit only a small degree of hysteresis at nearly all relative pressures, and in the isotherms of two further samples, hysteresis is exhibited only at intermediate relative pressures. These differences in the nature of the isotherms are attributed to variations in the rigidity of the mesoporous aggregate structures from one sample to another. This range of behaviour correlates well with variations found in the dispersion quality of the dye samples in water. © 1994 Elsevier Science B.V. All rights reserved.