The process of enzymatic degradation of the high-molecular hydroxyethyl-cellulose was followed by means of static low angle laser light scattering (static LALLS) which proved to be an excellent analytic method to obtain continuously an information about the decrease of the weight average molecular weight Mwwithout any manipulation of the substrate and enzyme, respectively. Moreover, due to the high sensitivity of LALLS the required substrate as well as enzyme concentration can be made much lower than needed for other physico-chemical techniques.