This Lecture was given with the object of explaining the preliminary steps to be taken in ascertaining the mortality experienced by a body of lives, commencing with the extraction of particulars from the records of individual cases and leading up to the point where the rates of mortality are calculated from the raw material (usually referred to as the unadjusted rates of mortality) before any smoothing process is adopted for the purpose of preparing monetary Tables based on the experience. The lecture was given with particular reference to the Mortality of Annuitants 1900–1920, the first report on which had just been published.