Optical waveguides are normally sensitive to the Surrounding media and also to the surface contaminations. The effective refractive index changes at the surface. Various sensor systems were developed based on this effect. One of the most sensitive and efffective methods is the optical waveguide lightmode spectroscopy (OWLS). At the same time. electrochemical methods are widely used both in inorganic and organic chemistry, and also advantages in microbiology were demonstrated. In this work, efforts are made and results are presented for the combination of these two methods for simultaneous measurement of refractive index and electrical Current changes caused by the presence of cells/molecules/ions to be investigated. An electrically conductive indium tin oxide (ITO) nanolayer is deposited and activated on the top of the OWLS planar waveguide oxide layer. ITO layers serve as working electrodes in the electrochemical measurements. The basic setup and an integrated system are demonstrated here. Measurements using H2O2 toluidine blue Solutions, and KCI and TRIS solutions as buffer and transport media are represented. Measurements show both the changes detected by the sensor layer and the effect of the applied potential in cyclic and chrono voltammetric measurements. Results demonstrate an effective combination of optical and electrochemical methods. (C) 2008 Elsevier B.V. All rights reserved.