Fluorescence was collected from cyanine-dye-impregnated arachidic acid monolayers at the air/water interface with the use of a fiber optics configuration and a Langmuir film balance. Fatty-acid-to-dye molar ratios in the monolayers ranged from 99:1 to 1:1. The monolayers were compressed in a step-wise manner, with sampling of cyanine fluorescence after each compression step. A drop in fluorescence intensity ranging from 20 to 80% was observed between the uncompressed and compressed monolayers. The observed fluorescence decrease appeared to be a function of barrier pressure rather than molecular area and dye concentration.