The concept of fungal succession is critically examined and illustrated with different examples from litter decomposition. Most fungi exhibit a mixed decomposition function. The importance of the total N content for decomposition in litter is discussed in relation to the C/N ratio. A tropical microflora has been delimited, partially at a species level, but some genera are more generally occurring in dry and hot climates, while others only occur in colder environments. An arctic flora has not been identified, but some strains have been found to exhibit optimal activity at low temperatures. Summaries of the micromycete work performed during IBP are presented for each of the biomes. Comparisons of fungal communities based on dominant species or through the use of diversity indices are discussed. Litter type, and to a certain degree climate and soil, is important for the composition of a specific fungal flora.-from Authors