SUMMARYThe Hyphomycetes,Aspergillus puniceus, A. ustusandFusarium solani, were isolated from enriched greenhouse soil, and shown to be capable of using the polyester, poly∊-caprolactone, as their sole carbon source. Possible synergistic and successional effects were studied. Statistical evaluation showed thatF. solaniwas initially the most effective decomposer of the plastic, but a spontaneous adaptive mutant ofA. ustus, which arose during the study, exhibited even higher activity. The monomer,∊-caprolactone, could also be used as sole carbon source byF. solaniand theA. ustusmutant.