Abstract. The viscoelastic behavior of aqueous oleyldimethylamineoxide (ODAO) solutions was examined by varying the concentration of ODAO, cD, and the average degree of protonation, , by adding hydrogen bromide to the system. ODAO forms long threadlike micelles in aqueous solution in spite of the absence of any additives. Therefore, the aqueous ODAO system shows pronounced viscoelastic behavior caused by entanglement between threadlike micelles as highly entangled polymer systems do. The frequency dependence of the storage and loss moduli for the system is perfectly described by that of a Maxwell model possessing only one set of relaxation time, , and strength, GN. GN is proportional to the square of cD as observed in concentrated liner polymer solutions, while decreases with increasing cD. On the other hand, the addition of HBr to control remarkably increases when GN is constant. This suggest that alters the inner structure of the threadlike micelles; association of head groups, dimers or trimers of ODAO are formed in the micelles owing to hydrogen bonding between protonated ODAO or between protonated and unprotonated ODAO. An increase in the number density of the associated head groups in the threadlike micelles increases . Moreover, the flexibility of the threadlike micelles in the system is not affected so much by a change in the number density of the associated head groups, since GN corresponding to the number density of entanglements in the system is kept constant.