Two laboratory trials were conducted to determine the effect of the addition of spores (conidia) of the nematophagous fungus, Arthrobotrys oligospora, on the development of the ruminant parasite, Strongyloides papillosus, in cultures of bovine faeces. Both studies showed that at a concentration of 2000 conidia/g faeces virtually eliminated infective larvae (> 99% reduction), following 14 days incubation under ideal conditions (25 degrees C and saturated humidity) for free-living development of this parasite species. In one trial, a high level of control was also observed at a 10-fold decrease in conidia concentration (200 spores/g faeces). This work has demonstrated, in principle, that A. oligospora could provide a practical biological control agent against S. papillosus infecting intensively raised young ruminants in the humid tropics/subtropics.