The successful immobilization and stabilization of a nitrile hydratase in the form of a cross-linked enzyme aggregate (CLEA^®) is described. CLEAs were prepared by using ammonium sulfate as an aggregation agent followed by cross-linking with glutaraldehyde. The effect of different glutaraldehyde concentrations on the recovery of enzyme activity in the CLEA and enzyme leakage from the CLEA matrix was investigated. Although activity recovery was low (21%) the CLEA facilitates easy separation and recycling of the nitrile hydratase. It was also found that the nitrile hydratase CLEA had substantially increased storage stability as well as increased operational stability during exposure to high concentrations of acrylamide and acrylonitrile compared to that of the nitrile hydratase in the crude cell-free extract and whole cell formulation.