The current status of Langmuir-Blodgett (LB) films is described with regard to biomimetic applications as separating membranes and sensor layers. In the first part, recent research activities on the utility of LB membranes for gas separation, liquid permeation, hyper- and ultrafiltration are reviewed. The morphological aspects of materials separation in LB films are discussed. In the second part, recent progress in the rapidly growing field of LB-film-based chemical sensors and biosensors is reviewed. The structure and function of gas and ion sensors, and enzyme and immunosensors is briefly discussed. Perspectives for future activities in the fields of LB membranes and sensors are outlined.