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The so-called two-step model has been applied to multifield 13C relaxation and NOE data to determine order parameters and correlation times of (decyldimethylammonio)propanesulfonate (DAPS) in pure and octanol-swollen DAPS micelles. Additional conformational information was obtained from 13C shift measurements above and below the critical micellization concentration. The combined results indicate that the zwitterionic headgroup is motionally restricted as compared to micellized ionic surfactant headgroups and that it is tilted relative to the normal of the micelle surface. Self-diffusion measurements demonstrate that micellar inclusion of octanol has large stabilizing effects of the DAPS micelle, decreasing the nonmicellized DAPS concentration dramatically. However, in the 13C relaxation and NOE data no significant differences in order parameters and correlation times of DAPS are detected in the presence of octanol. 13C shift measurements demonstrate, nevertheless, that minor conformational changes of the micellized DAPS molecule are induced by octanol.