The monolayer behavior at the air-water interface of a chiral nonlinear optical dye was evaluated. The dye alone, an ester of palmitic acid and 4-nitro-4'-[(3R)-hydroxypyrrolidino]-1,1'-azobis[benzene], did not form a stable monolayer at 23 °C at the air-water interface. However, mixtures of the dye with amylose acetate formed stable monolayers when the amount of the dye did not exceed 50 mol %. The surface structure of monolayers of the dye alone and of the mixtures was studied by transmission electron microscopy. This showed that molecular mixing did not occur. The mixtures are composed of domains of amylose acetate and two-dimensional crystallites of the dye molecules. The domains of the dye behave like H aggregates. It is argued that boundary lines between the crystallites of the dye and amylose acetate might play an important role of the stabilization process. As far as this study goes, the stabilization of the dye in mixed systems is only found for amylose esters as matrices.