Abstract The acid hydrolysis of cellulose and the cellulose derivatives hydroxyethyl cellulose, methyl cellulose and carboxymethyl cellulose have been investigated. The degradation was followed viscometrically and by end group analysis. It was found that the viscoxity‐molecular weight relationship deviated from the modified S TAUDINGER equation, the exponent a is increasing with decreasing molecular weight. The influence of acid concentration and temperature on the degradation rate was studied. It was found that the different cellulose derivatives exhibit quite similar degradation characteristics.