Various species of Antarctic macroalgae have been found to produce and release methyl halides at mean values of 34.7 pmol g-1 waw (wet algal weight) d-1 (methyl chloride), 1.98 pmol g-1 waw d-1 (methyl bromide) and 1.68 pmol g-1 waw d-1 (methyl iodide) into the seawater. Compared to temperate macroalgae, Antarctic macroalgae showed an approximately 10 to 50-fold lower release of these compounds. Due to the lower release and the restriction to the Antarctic region, Antarctic macroalgae may play a minor role in the global production of methyl halide, but have to be considered as biogenic contributors for methyl halides to the halocarbon budget in the Antarctic environment. Additional, investigated bromoform release, brominating activity and dimethylsulfoniopropionate (DMSP) concentrations detected in Antarctic macroalgae showed no correlation with methyl halides release rates. Therefore, a formation different to suggested enzymic pathways or origin from DMSP reacting with halides can be assumed. ¿ 1998 American Geophysical Union