The present invention relates to cross-linked cellulosic fiber having improved absorbency characteristics when compared to conventional cross-linked fibers. The cross-linked cellulosic fiber is obtainable by reacting pulp in the sheet or fluff form with one or more reagents selected from organic molecule having acid and aldehyde functional groups "acid aldehydes." The invention also relates to a method of producing the cross-linked fiber. The method includes heating the treated cellulosic fibers to promote intrafiber cross-linking. The cross-linked fibers are characterized by having an improved centrifuge retention capacity, fluid acquisition rate, resiliency, absorbent capacity, absorbency under load, and other absorbent properties. The inventive cross-linked fibers are useful in forming absorbent composites, and in particular absorbent cores for use in absorbent articles.