Abstract: A porous, hydrophilic, assimilable prosthesis is formed by the removal of solvent, without substantial dimensional change, from a solution of (a), an assimilable polymer composed primarily of polymerized units of an alpha or beta hydroxy carboxylic acid, preferably but not necessarily those having 1 to 4 carbon atoms, and (b), a small amount of a physiologically acceptable wetting agent that is sufficient to impart hydrophilicity to the prosthesis. The preferred assimilable polymer is a polylactic acid. The preferred process for making the prosthesis involves the lyophilization of a solution of polylactic acid having a molecular weight of at least 100,000, weight average, at a concentration of at least 31/2% by weight of the solution of the polylactic acid. A variety of physiologically acceptable wetting agents is useful, a preferred class being the alkali metal soaps of fatty acids or of alkyl aryl sulfonic acids.