The effect of passage through the earthworm gut on the viability of spores of saprotrophic fungi was found to vary depending on fungal and earthworm species. Of 5 fungal species fed to Lumbricus terrestris L., the spores of two (Fusarium lateritium Nees, and Agrocybe temulenta (Fries)) failed to germinate after gut passage, while germination of Trichoderma sp. and Mucor hiemalis Wehmer was significantly reduced. A similar fate was recorded for F. lateritium and M. hiemalis spores on passage through the gut of Aporrectodea longa (Ude), however in the case of Chaetomium globosum Kunze there was a significant increase in spore germination after transit through A. longa. The germination of spores of M. hiemalis increased after abrasion by soil particles in a peristaltic pump simulating the mechanical action of the earthworm gut. In contrast germination of this species was significantly reduced when spores were exposed to intestinal fluids from L. terrestris.