MgxZn1 O-x (x = 0.0-0.20) thin films have been deposited by sol-gel technique on glass substrates and the effect of growth ambient (air and oxygen) on the structural, and optical properties have been investigated. The films synthesized in both ambient have hexagonal wurtzite structure. The c-axis lattice constant decreases linearly with the Mg content (x) up to x = 0.05, and 0.10 respectively for air- and oxygen-treated films, above which up to x = 0.20, the values vary irregularly with x. The change in the optical band gap values and the ultraviolet (UV) peak positions of MgxZn1 O-x films show the similar change with x. These results suggest that the formation of solid solution and thus the structural and optical properties of MgxZn1 O-x thin films are affected by the growth ambient. (C) 2009 Elsevier B. V. All rights reserved.