Faecal samples of 52 hill cattle fed largely on oak leaves were screened for tannin-protein complex-degrading micro-organisms under different culture conditions using tannin-treated brain heart infusion agar medium. None of the animals were found to harbour tannin-protein complex-degrading enterobacteria. However, a fungus identified as Aspergillus niger van Tieghem having tannin-protein complex-degrading activity, was consistently isolated from the faeces of such animals. Optimum growth and sporulation was noticed under aerobic conditions at 30 degrees C on Czapek Yeast Agar medium.