Bacillus cereus isolated from soil, aerobically degraded starch-g-polyacrylonitrile (S-g-PAN). Extracellular peroxidase activity reached maximum after 3 h and this probably initiated the depolymerisation of polyacrylonitrile chains of S-g-PAN to the free monomer, acrylonitrile (AN). The conversion of free AN to acrylamide and acrylic acid was catalysed by intracellular nitrile hydratase and amidase, respectively. The concentration of the former increased with increased induction by AN. The maximum degradation of added S-g-PAN (0.64%) and AN (0.32%) to the culture broths separately occurred after 6 h of bacterial growth, respectively, with the corresponding formation of acrylamide (0.19 and 0.26%) and acrylic acid (0.13 and 0.19%). After 48 h of growth neither acrylamide nor acrylic acid could be detected indicating their complete utilisation. Addition of FeSO4·7H2O to the medium increased the specific activity of nitrile hydratase. Extracellular α-amylase activity was maximal after 8 h of growth and degraded the starch moiety to low molecular weight dextrin-type products.