The brown macroalga Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, Druehl & G.W. Saunders (formerly Laminaria saccharina[L.] Lamouroux) was exposed to ultraviolet radiation (UVR) in the mW UV-A and mW UV-B range in the laboratory for up to 28 days. The release rates of volatile organohalogens, such as chloroform, bromoform, dibromomethane and methyl iodide, were determined. From these rates, the total emission of reactive organic halogens was calculated. The results revealed that exposure to UVR significantly affected the emission of reactive organic halogens by the macroalga under investigation. An increase in the release of reactive organic iodine was observed for the algal species. In contrast, for reactive organic bromine and reactive organic chlorine, a decrease in emission by the macroalga was observed. Apparently, the potential for increased levels of UVR resulting from further ongoing destruction of the stratospheric ozone layer may increase the importance of marine macroalgae in atmospheric reactions involving organic halogens.