An aqueous biodegradable polymeric drug delivery composition possessing reverse thermal gelation properties comprised of an aqueous phase having uniformly contained therein: (a) an effective amount of a drug; and (b) a biodegradable AB type di block copolymer comprising: i) 61 to 85 % by weight of a biodegradable, hydrophobic A block which is a member selected from the group consisting of biodegradable polyesters, biodegradable polyester amides, biodegradable polyether esters, biodegradable polyurethanes, biodegradable polyester urethanes, biodegradable polycarbonates and polyester carbonates; and ii) 15 to 39 % by weight of a biocompatible, hydrophilic B block comprising a mono functional polyethylene glycol, wherein, each hydrophobic A block has a number average molecular weight of between 1000 Daltons and 4000 Daltons and each hydrophilic B block has a number average molecular weight of between 500 Daltons and 800 Daltons; and wherein said di block copolymer has a number average molecular weight within a range of 450 Daltons to 15000 Daltons and wherein the copolymer possesses reverse thermal gelation properties such that it exists as a solution at about 5-34°C in water, but at 37°C, the copolymers spontaneously interact to form a semisolid hydrogel. (a) an effective amount of a drug; and (b) a biodegradable AB type di block copolymer comprising: i) 61 to 85 % by weight of a biodegradable, hydrophobic A block which is a member selected from the group consisting of biodegradable polyesters, biodegradable polyester amides, biodegradable polyether esters, biodegradable polyurethanes, biodegradable polyester urethanes, biodegradable polycarbonates and polyester carbonates; and ii) 15 to 39 % by weight of a biocompatible, hydrophilic B block comprising a mono functional polyethylene glycol, wherein, each hydrophobic A block has a number average molecular weight of between 1000 Daltons and 4000 Daltons and each hydrophilic B block has a number average molecular weight of between 500 Daltons and 800 Daltons; and wherein said di block copolymer has a number average molecular weight within a range of 450 Daltons to 15000 Daltons and wherein the copolymer possesses reverse thermal gelation properties such that it exists as a solution at about 5-34°C in water, but at 37°C, the copolymers spontaneously interact to form a semisolid hydrogel. i) 61 to 85 % by weight of a biodegradable, hydrophobic A block which is a member selected from the group consisting of biodegradable polyesters, biodegradable polyester amides, biodegradable polyether esters, biodegradable polyurethanes, biodegradable polyester urethanes, biodegradable polycarbonates and polyester carbonates; and ii) 15 to 39 % by weight of a biocompatible, hydrophilic B block comprising a mono functional polyethylene glycol, wherein, each hydrophobic A block has a number average molecular weight of between 1000 Daltons and 4000 Daltons and each hydrophilic B block has a number average molecular weight of between 500 Daltons and 800 Daltons; and wherein said di block copolymer has a number average molecular weight within a range of 450 Daltons to 15000 Daltons and wherein the copolymer possesses reverse thermal gelation properties such that it exists as a solution at about 5-34°C in water, but at 37°C, the copolymers spontaneously interact to form a semisolid hydrogel. wherein, each hydrophobic A block has a number average molecular weight of between 1000 Daltons and 4000 Daltons and each hydrophilic B block has a number average molecular weight of between 500 Daltons and 800 Daltons; and wherein said di block copolymer has a number average molecular weight within a range of 450 Daltons to 15000 Daltons and wherein the copolymer possesses reverse thermal gelation properties such that it exists as a solution at about 5-34°C in water, but at 37°C, the copolymers spontaneously interact to form a semisolid hydrogel.