In November-December 1986 and October 1987 a comparative investigation of the invertebrate community of a number of soil types in dry savannahs was conducted in Gambela Province (= Illubabor Prov.) SW-Ethiopia during dry and rainy seasons. The dry season is characterised by a gradual decrease of biological activities with certain groups of macrofauna passing it in a resting stage (diapause egg) and some others migrating into more humid habitats. During the rainy season most groups of soil macrofauna are active with a considerable rise in population density in a number of soil types and a fall in partly submerged soils. Based on the data obtained at least two phenomological aspects in the soil population of savannahs should be considered: dry and rainy. Regular fires leave their mark on the trophic structure of the soil population: all the soils lose individuals from the saprotrophous complex (except for termites). In the dry and rainy season the relative abundance of predators and phytophages rise respectively. The trophic structure of macrofauna complexes in relation to soil humidity is described. Judging from both faunal composition and abundance of soil invertebratesw the tropical ferralitic soils seem to be potentially highly productive.