A protein extract containing ficin was immobilized on glyoxyl agarose at pH 10 and 25 degrees C. The free enzyme remained fully active after 24 h at pH 10. However the enzyme immobilized on the support retained only 30% of the activity after this time using a small substrate. After checking the stability of ficin preparations obtained after different enzyme-support multi-interaction times, it was found that it reached a maximum at 3 h (40-folds more stable than the free enzyme at pH 5). The immobilized enzyme was active in a wide range of pH (e.g., retained double activity at pH 10 than the free enzyme) and temperatures (e.g., at 80 degrees C retained three-folds more activity than the free enzyme). The activity versus casein almost matched the results using the small substrate (60%) at 55 degrees C. However, in the presence of 2 M of urea, it became three times more active than the free enzyme. The immobilized enzyme could be reused five cycles at 55 degrees C without losing activity.