SummaryAmmonia emissions contribute to acidification in Europe. The major emission sources are livestock and fertiliser use. This study presents the costs of controlling ammonia emissions in 33 regions in Europe. Abatement options include low nitrogen feed, stable adaptations, covering manure storage, cleaning stable air, and low ammonia applications of manure. Cost estimates are based on country- and technology-specific data. Variations in average costs, and the structure of livestock population and fertiliser use, cause considerable differences in costs between countries for applying similar reductions ortechniques. Allowing countries to choose their own mix of control options would be more cost-effective