To come up to the demand for extremely sensitive biosensors for parallel real-time bioanalyses, we present several configurations of label-free biosensors on Silicon-on-Insulator (SOI) optical chips. We discuss results on microring resonators with a non-fouling polymer coating, increased sensitivity with slotted wire resonators and the design and fabrication of an integrated surface plasmon resonance interferometer. The high refractive index contrast of SOI offers submicron-size features with high quality for dense integration, high sensitivity and detection with very low analyte volumes. The fabrication method, 193nm deep-UV lithography, allows for mass production of cheap disposable biochips.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.