The creation of large-sized magnetic islands through excitation of neoclassical tearing modes (NTMs) and the concommitant degradation of energy confinement is a major concern for ITER. The basic physical mechanisms governing the dynamics of this instability are introduced, and important experimental observations and techniques of controlling or suppressing these modes are briefly reviewed. The effects of plasma rotation on the excitation threshold and saturated island sizes of NTMs, as observed in many recent experiments, and their present understanding as obtained from model analytical and numerical simulations are discussed.
