We have used dynamic and static light scattering to study rodlike micelles of C(12)E(6) in H2O. Nine surfactant concentrations, C, in the range 3 < C < 510 mg/mL and in the temperature, T, range 15 < T < 50 degrees C were studied. The mean diffusion coefficient, determined using dynamic light scattering, shows a well-defined minima as a function of concentration along each isotherm. The concentration at which the minimum occurs is temperature dependent and to a very good approximation marks the threshold crossover concentration from dilute to semidilute solution behavior. From these data, using the recent theory of Carale and Blankschtein (J. Phys. Chem. 1992, 96, 459), we determine the persistence length, a measure of micellar flexibility, as a function of temperature. It obtains a value of 15 nm near 20 degrees C and 6 nm near 50 degrees C. From static light-scattering measurements we determine the characteristic length which can be interpreted as a pore size in semidilute solutions. This quantity shows a maximum at concentrations near where the diffusion coefficient obtains a minimum. From this measurement the persistence length is also determined. By comparison of theoretical expressions with these measurements and the dynamic light-scattering measurements the persistence length was also deduced. This determination of the persistence length is essentially temperature independent with a value of approximately 2 nm.