Abstract: A leak detectable refrigeration composition comprising an effective amount of a fluorescent, alkyl substituted perylene dye dissolved in a refrigeration oil and a polyhalogenated hydrocarbon refrigerant, is prepared for use in refrigeration systems in automobile air conditioning systems, commercial refrigeration systems, and the like. Upon exposure to ultraviolet light, there is sufficient fluorescence by the refrigeration liquid to allow one to visually detect a leak in the system due to the presence of the dye at the source of the leak. Small leaks which were previously nondetectable with dye coloring systems detectable in normal light may now be detected due to the greater visibility of the fluorescent dye under an ultraviolet light.