We present a prototype of a Foucault-Like Wavefront Sensor (FLWS) that will be implemented in the Adaptive Optics Systems of 3.5m TNG and is of the proposed choices for the 2 X 8.4m LBT. The FLWS has some interesting features for Adaptive Optics applications: it has a linear relationship between measured signals and wavefront derivatives like the Shack-Hartmann sensor, it allows to change on the fly the gain used for wavefront measurements like the Curvature Sensor, and finally it allow to modify easily the wavefront aberration spatial sampling. The developed prototype of the FLWS is described and first laboratory results are presented. Measurements of static wavefront aberrations performed by the FLWS and a Wyko interferometer are compared to test the accuracy of the sensor, giving an error of a few tens of nm in terms of reconstructed wavefront rms, when aberrations of typical atmospheric turbulence strength are induced.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.