The paper discusses turbine-generator rotor forgings. It includes a brief history of the development of present designs, materials used, manufacturing methods, and the various testing practices employed. Special reference is made to low-pressure rotor construction. A discussion on types of instability encountered in turbine rotors is included. The paper includes a section on design criteria dealing with static considerations, fatigue considerations, and reports the results of several model bursting tests. The importance of proper alignment of rotor shafts is covered.