Magnetite/activated carbon composite (MAC) and MAC modified with poly (N-isopropyl acrylamide) (PNIPAM) (PMAC) were synthesized as dye adsorbents, and their structures were evaluated by inductively coupled plasma atomic emission spectrometry, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption-desorption measurement. As a result, PMAC was found to consist of 16.9 wt% of magnetite loaded on the activated carbon, with 7.6 wt% of PNIPAM modifying the MAC. The amounts of methyl orange (MO) adsorbed by activated carbon, MAC, PMAC (room temperature) and PMAC (50 degrees C) were 271, 285, 178 and 273 mu mol/g, respectively. The adsorption of MO by PMAC was remarkably lower at room temperature than at 50 degrees C, which was almost the same as that of activated carbon and MAC. The activated carbon, MAC, PMAC were dispersed in water at room temperature, while PMAC precipitated in water at 50 degrees C. PMAC is effective for dye adsorption, and it self-aggregates above LCST, so it is expected to be effective for recovery by magnetic separation.