Speed of sound, u, of dodecyltrimethylammonium bromide (DTAB) aqueous solutions has been determined at 295.15, 302.15 and 309.15 K. The speeds of sound, u, data have been used to estimate isentropic compressibility, K s , apparent molal isentropic compressibility, φ k(s), acoustic impedance, Z, molal sound of speed, R m , and relative association, R A , of DTAB in aqueous solution. These parameters have been interpreted in terms of solute-solute and solute-solvent interactions and micellar behavior of DTAB.