AbstractThree high molecular weight polycaprolactones (M̄w= 35,000, 18,600, and 7,130) were utilized as the sole carbon source by five of six fungi tested by the American Standards for Testing and Materials (ASTM) agar plate method. The fungi wereAspergillus flavus, A. niger, A. fumigatus, Chaetomium globosum, Pencillium funiculosum, and aFusarium sp.Quantitative analysis of degradation was performed using gel permeation chromatography (GPC). GPC analysis demonstrated differences between the activities of organisms which appeared similar by the ASTM method, and showed that, while all molecular weight species within each polymer were hydrolyzed, in several cases low molecular weight end products were not assimilated. Depending on the organism, the dominant factor determining degradability was either polymer molecular weight or degree of crystallinity.