Abstract: A tissue-filling composition comprises an injectable material having the properties of a Bingham plastic. The tissue-filling composition is a solid which partially liquefies as it is injected through a needle or cannula into solid tissue. The tissue-filling composition may be a poly(vinyl alcohol) produced from an aqueous solution which is subjected to a single freeze-thaw cycle under conditions which cause the poly(vinyl alcohol) to have the properties of a Bingham plastic.