Abstract: Hydroxyalkyl starch having utility as a cryoprotective agent for human errocytes and as a plasma volume expander is prepared by the steps of subjecting a waxy starch to acid hydrolysis at a temperature below the gelatinization temperature of the starch to effect a molecular size reduction while substantially retaining the granular form of the starch, reacting the hydrolyzed starch with a reducing agent under reaction conditions which prevent the dissolution of the granular starch, suspending the stabilized, hydrolyzed starch in a liquid medium comprising a water-miscible organic solvent, in which medium the hydrolyzed starch is substantially insoluble, reacting the stabilized, hydrolyzed starch in suspension with a starch hydroxyalkylating agent under basic pH conditions until a hydroxyalkylated starch having a molecular substitution within the range from about 0.3 to 0.9 is obtained. The granular form of the starch is retained throughout the process.