Antiamoebins I, III and XVI as well as several others in minor amounts were produced by four strains of the coprophilous fungus Stilbella erythrocephala (syn. S. fimetaria) in its natural substrate and in liquid culture. The total antiamoebin concentration in dung was 126-624 microg g(-1) fresh weight, with minimum inhibitory concentrations against most other coprophilous fungi being at or below 100 microg mL(-1). Myrocin B, not previously described from S. erythrocephala, was also produced, but only at low, nonfungicidal levels (< 5.3 microg g(-1)). No other antifungal substances were detected. It is concluded that antiamoebins are responsible for antibiosis in dung colonized by S. erythrocephala.