Stack, chimneylike, and threadlike assemblies have previously been proposed for the structure of disodium cromoglycate (DSCG) aggregates in aqueous solutions. The results of the synchrotron x-ray scattering investigations reported here reveal the formation of simple columnar assemblies with π-π stacking at a separation of 3.4 A between the DSCG molecules. Lateral separation between the assemblies is concentration ˚ and temperature dependent, varying from 35 to 42 A in the orientationally ordered nematic ( ˚ N) phase and from 27 to 32 A in the columnar or middle ( ˚ M) phase having long range lateral positional order. The assemblies’ length depends on concentration and consists of 23 molecules in the N phase, becoming three to ten times larger in the M phase. The scission energy is concentration dependent in the N phase with values 7.19 ± 0.14 kBT (15 wt %), 2.73 ± 0.4 kBT (20 wt %), and 3.05 ± 0.2 kBT (25 wt %). Solutions of all concentrations undergo a spinodal decomposition at temperatures above 40 °C, resulting in DSCG-rich regions with the M phase and water-rich regions in the N and isotropic phases. DO