Abstract: A method of preparing a therapeutically active crystalline form of glucosamine sulphate which is stable at ambient temperature and humidity and corresponds to the empirical formula: ##STR1## in which M represents a metal selected from the group consisting of Na, K, Ca, Mg,x=1 if y=2, andx=2 if y=1,wherein glucosamine hydrochloride and a sulphate of a metal selected from Na, K, Ca, Mg are reacted in the stoichiometric ratio defined by formula (I), in an aqueous solvent, and the stable crystalline form is precipitated by the addition of a liquid precipitating agent miscible with water.