Diffusing wave spectroscopy has been used to measure the rheological behavior of pullulan (M-w = 1 x 105) aqueous solutions up to concentration of 40 g/dL. It was found that these solutions were mainly viscous, with the loss modulus G" higher than the elastic modulus G'. The plot of the specific viscosity eta(sp) as a function of pullulan concentration showed two critical concentrations c * = 4 g/dL and c ** = 15 g/dL. For c < c *, eta (sp) approximate to c(1.25 +/- 0.05); for c * < c < c **, eta sp approximate to c(2 +/- 05); and for c > c **, eta (sp) approximate to c(4.5 +/- 0.5). These results are in very good agreement with those reported in the literature.