This chapter describes common procedures for both Internal Through and True-Through calibration using Anritsu AutoCal® modules including the 36585-Series Precision AutoCal Modules and the 36581KKF Standard AutoCal Module. This chapter provides two examples of using a precision adapter with an AutoCal unit to create difference-gender reference planes as is adapter removal with an AutoCal unit. The chapter concludes with user-based AutoCal module characterization and working with older Anritsu AutoCal units.