Three techniques of acid hydrolysis are verified for their ability to efficiently hydrolyse freshwater polysaccharides. Polysaccharides isolated from two eutrophic lakes were hydrolysed rapidly as compared to model or marine polysaccharides. No single technique is 100% satisfactory for all polysaccharides (i.e. complete hydrolysis with no degradation). Hydrolysis by 0.1 M HCl appeared to give the best results while acceptable results were also obtained for 1.2 M H₂SO₄. The results suggest that it is prudent to hydrolyse freshwater polysaccharides under the least drastic conditions and for as short of a time as possible in order to minimize decomposition of the sample, (esp. uronic acids). Interferences due to humic acid; did not appear to increase as a function of hydrolysis time.