the invention is directed to a method of making carboxylated cellulose fibers whose fiber strength and degree of polymerization is not significantly sacrificed . the method involves the use of tempo as a primary oxidant and a hypohalite salt as a secondary oxidant in an aqueous environment . preferably the oxidized cellulose is then stabilized against d . p . loss in alkaline environments and color reversion with a reducing agent such as sodium borohydride . alternatively it may be treated with an oxidant such as sodium chlorite . the method results in a high percentage of carboxyl groups located at the fiber surface . the product is especially useful as a papermaking fiber where it contributes strength and has a higher attraction for cationic additives . the product is also useful as an additive to recycled fiber to increase strength . the method can be used to improve properties of either virgin or recycled fiber . it does not require high α - cellulose fiber but is suitable for regular market pulps .