We present experimental and numerical results of current-driven magnetization switching in magnetic tunnel junctions. The experiments show that, for MgObased magnetic tunnelling junctions, the tunnelling magnetoresistance ratio is as large as 155% and the intrinsic switching current density is as low as 1.1 × 10 6 A cm −2. The thermal effect and current pulse width on spin-transfer magnetization switching are explored based on the analytical and numerical calculations. Three distinct switching modes, thermal activation, dynamic reversal, and precessional process, are identified within the experimental parameter space. The switching current distribution, write error, and read disturb are discussed based on device design considerations. The challenges and requirements for the successful application of spin-transfer torque as the write scheme in random access memory are addressed.