This paper aims to set forth the criteria that are important in the design of certain servomechanisms and to show how certain analytical procedures can be applied to almost any problem to define quantitatively the properties that the control should have in order to make the servomechanism perform in the manner desired. The nomenclature used is essentially that proposed by Draper (1). It is used in the treatment of the problem of synthesizing a controller for a servomechanism whose controlled member is to be rotated and can be defined in terms of inertia plus viscous and coulomb friction, plus a load torque. The broad objective of the designer is assumed to be that of designing a controller which will keep the dynamic error in controlled angular position of the controlled member a minimum under certain operating conditions. The transient and steady-state error for certain forms of motion, the criteria for stability, the effects of viscous friction, coulomb friction and load torques on the desired performance, and other related matters are treated. Several nondimensional charts and tables are included in the paper and show quantitatively the performance of any particular servomechanism with a controlled member of the kind treated, when the system has the various forms of control.