The two-dimensional nuclear Overhauser enhancement spectroscopy (2D NOESY), H-1 NMR chemical shift, and spin-lattice and spin-spin relaxation measurements of aqueous solution of various molar ratios of sodium dodecyl sulfate (SDS) to Triton X-100 (TX-100) from 0.27 to 8.0 give some detailed structure of the mixed micelles formed. The appearance of cross peaks between the protons of SDS and those of TX-100 in the 2D NOESY map is direct evidence for the solubilization of the hydrocarbon chains of SDS inside the TX-100 micelles that have nonextended hydrocarbon chains. The effect of the aromatic ring currents of TX-100 on the protons of the methylene groups, which are nearest to the polar head of SDS, indicates the near vicinity of these groups. The existence of the cross peaks between the hydrophilic protons and the remote hydrophobic protons of TX-100 suggests that the hydrophilic chains are not extended in the mixed micelles. 1H spin-lattice relaxation time (T-1) and spin-spin relaxation time (T-2) measurements support the results obtained by the 2D NOESY experiments.