The invention relates to compositions suitable for plasma substitution comprising as a plasma expander a recombinant gelatin-like protein. Characteristic is that the gelatin-like protein can be a monomer or a polymer like a dimer, trimer or a tetramer of a human recombinant gelatin-like protein having an isolectric point of less than 8. The resulting gelatin-like proteins provide a method to control the clearance rate of a plasma expander by its molecular weight. Preferably the gelatin-like proteins have a low hydroxyproline content which prevents the composition from gelling and thus allows the use of high-molecular weight proteins in order to establish a suitable colloid osmotic pressure. An additional advantage of the gelatin-like proteins is that these avoid the risk of anaphylactic shock that exists in conjunction with the use of commercially available preparations.