The milk-clotting enzyme found in the flowers of Cardo (Cynara cardunculus) was investigated as to its suitability as a substitute for traditional animal rennet used in cheese-making. The influence of milk pH, temperature and quantity on the clotting activity of this enzyme was studied. Rheological behaviour of cow'smilk and sheep-milk curds, from renneting to cutting, was determined with the Plint cheese curd torsiometer for various Ca contents and pH values. Edam, Serra and Roquefort cheeses were made and the protein breakdown which occurred in the cheese during the ripening period was determined. Animal rennet was used as a control in all the experiments. The enzyme from Cardo was a satisfactory substitute for animal rennet with cow's milk and was even more suitable for sheep's milk. It was found to be a very good clotting enzyme for soft-bodied cheese like Serra, but because of its high proteolytic activity it presented some problems in Edam cheese-making. In Roquefort cheese it gave satisfactory results, but with some loss in yield.