Aggregation of the following surfactant series in D2O has been studied by H-1 and C-13 NMR spectroscopy: RCONH(CH2)(2)N+ (CH3)(3)Cl-, where RCO is an acyl group containing 10-16 carbon atoms. Micelle formation has been followed by measuring observed chemical shifts, delta(obs), and apparent transverse relaxation times, 1/T-2*, of the surfactant discrete groups as a function of surfactant concentration, below and above its critical micelle concentration, cmc. Plots of delta(obs) and/or 1/T-2* versus [surfactant] are sigmoidal and were fitted to a model based on the mass-action law. A modified computation procedure was introduced in order to calculate the following: cmc; the equilibrium constant of micelle formation, K, the micelle aggregation number, N-agg; and the chemical shifts of the monomer, delta(mon), and the micelle, delta(mic), respectively. The modification introduced permits simple and accurate calculation of he above-mentioned micellar parameters from the same set of experimental data. NMR-based cmc and N-agg values are in excellent agreement with those previously determined by independent techniques. K and Nagg increase as a function of increasing the length of the surfactant hydrophobic tail. Gibbs free energies of micellization, DeltaGdegrees(mic), were calculated and divided into contributions from the CH2 groups in the hydrophobic chain and from the (terminal CH3 + headgroup). Both quantities agree with those previously calculated from conductivity data. The contribution of the (terminal CH3 + headgroup) to DeltaGdegrees(mic) shows the importance to micellization of direct and/or water-mediated H-bonding of the surfactant amide group. Comparison of (delta(mic) - delta(mon)) with data in bulk solvents (CDCl3 and CD3OD/D2O, respectively) shows that the monomers are probably not fully exposed to D2O below the cmc, in agreement with previous NMR investigations of cationic surfactants.