This article presents an overview of common heat treating problems arising due to poor part design, material incapabilities, difficult engineering requirements, incorrect heat treatment practice, and nonuniform quenching with emphasis on distortion and cracking of quenched and tempered steels. It provides useful information on selection of steels for heat treatment, and discusses the causes of residual stresses, distortion (size and shape), and size changes due to hardening and tempering. The article elucidates the control techniques for such distortions. It describes the importance of decarburizing, and discusses the problems caused by heating, cracking, quenching, typical steel grades, and design.