An evaluation of the individual effects of five standard test fungi and one known to degrade polyurethanes was carried out using the methodology of International Organization for Standardization (ISO) 846. Growth of the fungi on a polycaprolactone polyurethane as the sole carbon source was compared with the growth in the presence of glucose and malt extract plus peptone. Visual assessments, surface effects, and changes in the mechanical properties were determined. Of the five tested, three of the standard test fungi gave ratings indicating no nutritive value. The other two and <i>Gliocladium roseum</i> gave ratings indicative of the presence of nutrients in the polyurethane. With the exception of <i>G. roseum</i>, no correlation could be shown between the visual assessments and the changes in mechanical properties. This was also statistically reflected in the lack of difference between the loads recorded at 100% and ultimate elongation of the samples when compared with sterile controls. <i>G. roseum</i> again was the only exception to this observation.