In this article we present the spectral and nonlinear optical properties of ZnO-TiO2 nanocomposites prepared by colloidal chemical synthesis. Emission peaks of ZnO-TiO2 nanocomposites change from 340 nm to 385 nm almost in proportion to changes in E-g. The nanocomposites show self-defocusing nonlinearity and good nonlinear absorption behaviour. The nonlinear refractive index and the nonlinear absorption increase with increasing TiO2 volume fraction at 532 nm and can be attributed to the enhancement of exciton oscillator strength. ZnO-TiO2 is a potential nanocomposite material for the tunable light emission and for the development of nonlinear optical devices with a relatively small limiting threshold. (c) 2008 Elsevier Inc. All rights reserved.