A complementary discussion is given of an earlier presented theory for viscometric determination of enzymic activity towards polymer substrates. Five different, purified endo-1,4-beta-glucanases from the fungus Sporotrichum pulverulentum have been characterised with respect to their molecular activities(Am) and Michaelis-Menten constants (Km). The errors in the Am and Km values are discussed. The Am value seems to be more valuable as a distinguishing parameter than the Km value.