Optically transparent polyimide:titanium dioxide (TiO2) composite waveguide materials were prepared by the dispersion of nano-sized TiO2 particles into polyimide. The particles were produced through reverse micelles using the sol-gel method, and were dispersed into the fluorinated polyimide solution. The solution was coated on a glass substrate, and a polyimide : TiO2 composite waveguide (4 wt % TiO2 concentration) was successfully produced after the heat treatment. Because the particle size was very small, no noticeable scattering loss was observed in the resultant slab waveguide. The measured optical propagation loss at 633 nm was 1.4 dB cm(-1). It is equivalent to that of the pure polyimide, and the refractive index was increased from 1.550 to 1.560 by the incorporation.