Micellar aggregates of the nonionic peptide derivative Boc-Leu-Asn-OCH2CH3 (1) have been observed in aqueous solution, Evidence for micelle formation of the above peptide was obtained by conductometric and fluorescence spectroscopic techniques. Keto-enol tautomeric ratio of benzoylacetone was taken for the determination of critical micelle concentration (cmc). From the values of critical micelle concentration of the above peptide Delta G(m)(0), Delta H-m(0), Delta S-m(0) and Delta C-p(0) have been estimated, and it was found that there are two processes with regard to these parameters. In both the processes, the prime cause for aggregation seems to be the stability of the micelle due to the enthalpic contribution. The spherical micellar model was used to explain the aggregation number and the thermodynamic parameters.