A new approach to the fabrication of magnetic thermosensitive microcontainers of Fe(3)O(4) nanoparticles with poly(N-isopropylacrylamide) walls is presented. The microcontainers undergo a temperature-induced volume phase transition and present an impressive magnetic response. The microcontainers have a well-defined structure with a narrow size distribution. The wall thicknesses of the microcontainers can be controlled according to requirements. Compared to other preparation methods, the process is simple and reproducible. The magnetic saturation of these microcontainers is high enough to meet most requirements of bioapplications. To further investigate the potential application of these microcontainers, they are tested as drug carriers, with the drug loading and releasing processes carefully studied. The drug encapsulation efficiency and drug content in the carriers are pH-dependent, and the carriers have a maximal drug loading of about 50 wt% under alkaline conditions. The release of the drug from the microcontainers can be controlled by the environmental pH, temperature, and magnetic force.