Aqueous mixtures of the two alkyl glucosides n-nonyl beta-glucoside (C(9)G(1)) and n-decyl beta-glucoside (C(10)G(1)) have been studied. The phase diagram of the ternary C(9)G(1)/C(10)G(1)/water system in the water rich corner has been determined and is discussed in relation to the binary C(9)G(1)/water and C(10)G(1)/water phase diagrams. The latter two diagrams are significantly different in the dilute surfactant regime with a broad two-phase region in the C(10)G(1)/water system that is not present in the C(9)G(1)/water system. The evolution of the microstructure in the micellar solutions has been determined by means of NMR self-diffusion measurements both at a constant total surfactant concentration when the C(9)G(1)/C(10)G(1) ratio is varied and at constant C(9)G(1)/C(10)G(1) ratio when the total surfactant concentration is varied. From the results presented, it is suggested that the microstructure in the solution phase of the C(9)G(1)/C(10)G(1)/water system changes from discrete micelles at low concentrations toward a bicontinuous structure of interconnected rods as the concentration increases. A mechanism behind the phase separation in the C(10)G(1)/water system is also proposed and discussed.