The proper application and use of turbine supervisory instruments is becoming more important owing to centralization of controls at remote points from the power-generating equipment and also the growing trend of power companies to quick-start their machines. Equipment is available to record turbine conditions in terms of shell and differential expansion, speed and camshaft position, bearing vibration, and shaft eccentricity. A description of shell and differential-expansion recording equipment is included. The value of the instruments depends upon the proper interpretation of the records. A feature of the paper is a discussion of a number of case examples in which mechanical trouble in the turbine or generator was detected by the instruments.