Thermo- and pH-responsive micellization of poly(ethylene glycol)-b-poly(4-vinylpyridine)-b-poly(N-isopropylacrylamide) in water was studied. Micellization of the triblock copolymer, which was synthesized by sequential atom transfer radical polymerization of 4-vinylpyridine and N-isopropylacrylamide, occurred with combined stimulus of temperature and pH changes to form various morphological micelles. The copolymer existed as unimers at pH 2.0 and then associated into spherical core-corona micelles when pH increased from 2.0 to 6.5 at 25 degrees C. The critical aggregation temperature of the copolymer was about 34.6 degrees C, which was a little higher than poly(N-isopropylacrylamide). When the copolymer solution was heated above the critical aggregation temperature, the copolymer first self-assembled into compound core-corona micelles or micellar cluster and then converted into core-shell-corona micelles with pH increasing from 2.0 to 6.5. When temperature decreased from 50 to 25 degrees C, the core-shell-corona micelles further rearranged into core-corona micelles.