The wormlike micelles formed with the surfactant pentaoxyethylene decyl ether C10E5 containing n-dodecanol were characterized by static (SLS) and dynamic light scattering (DLS) experiments. The SLS results have been analyzed with the aid of the light scattering theory for micelle solutions, thereby yielding the molar mass M-w(c) as a function of concentration c along with the cross-sectional diameter d of the micelle. The observed Kc/Delta R-0 as a function of c and the hydrodynamic radius R-H as functions of M-w have been well described by the theories for the wormlike spherocylinder model. It has also been demonstrated that the apparent hydrodynamic radius R-H,R-app(c) as a function of c is well described by a fuzzy cylinder theory which takes into account the hydrodynamic and direct collision interactions among micelles. Our previous results for the hexaoxyethylene dodecyl ether C12E6 micelles containing n-dodecanol were reanalyzed in the same scheme. It has been found that the micellar length increases with increasing concentration c or with raising temperature T irrespective of the composition of the C10E5 + n-dodecanol and C12E6 + n-dodecanol systems. The length of the micelles at fixed c and T steeply increases with increasing weight fraction w(d) of n-dodecanol in both systems. The growth of the micelles accompanies the increase of the cross-sectional diameter d of the micelles and the results that the surfactant molecules are more densely assembled with increasing w(d) in order to keep n-dodecanol molecules inside the micelles.