This paper describes the application of Langmuir-Blodgett type layers in planar optical sensors for chemical parameters including alkali ions, oxygen, halides and pH. The major advantages of LB layer based sensors are the ease of reproducible fabrication, a well-defined layer thickness, and usualy quite short response times. In addition, it offers analytical possibilities not provided by thick film techniques. As a result, potentiometric measurement of boundary potentials using electrochromic dyes have become possible. On the other hand, the type of bilayers used so far is prone to mechanical disruption, and poor signal-to-noise ratios are observed. Potential future techniques will include polymeric lipid membranes, the evanescent wave technique for gathering more intense signals, and the coupling of LB techniques to fiber optic waveguides.