The phase behavior of the Triton X-100/poly(acrylic acid) aqueous system within the entire range of surfactant concentration and up to 30 wt % polymer was examined at various temperatures. At 25 degrees C two isotropic solution phases (L-1 and L-2) and one hexagonal liquid crystalline phase form in the ternary system. The hexagonal liquid crystalline and the isotropic solution phases were characterized by means of PGSE-NMR, SAXS, and rheological measurements. The presence of the polymer changes the melting temperature rather than the SAXS lattice spacing of the hexagonal liquid crystalline phase. Self-diffusion studies in the isotropic solution region show that surfactant diffusion is slower when polymer is added. The obtained data show that surfactant and polymer associate; the polymer molecules are probably adsorbed on the surface of the surfactant aggregates.