Litter decomposition is controlled by three main factors: climate, litter quality and the nature and abundance of the decomposing organisms. Climate is the dominant factor in areas subjected to unfavourable weather conditions, whereas litter quality largely prevails as the regulator under favourable conditions. Litter quality remains important until the late decomposition stages through its effects on humus formation. Interest in the role of litter decomposition in the global carbon cycle has increased recently since (1) increased atmospheric carbon dioxide will probably affect the chemical quality of litter (especially nitrogen content), and (2) global warming may enhance decomposition rates. Copyright © 1995. Published by Elsevier Ltd.