In this paper the optical-functional properties of integrated-optical waveguides in a planar polymer chip prepared by UV-Iaser irradiation have been investigated. Particularly the refractive index distribution of the waveguide is examined by a two-beam interferometric method. Also the waveguiding effect of this integrated-optical structure has been proved. The study shows that the refractive index depth profile strongly depends on the UV-irradiation dose. Several mostly independently occurring photochemical processes competing with one another can explain the formation and shape of the refractive index distribution. (C) 2004 Elsevier B.V. All rights reserved.