The usual method of conducting ships’ speed trials is for the ship to make runs over a measured mile. Recently, however, sea trials have been carried out using other methods, which seem to offer certain advantages. The trials of the S.S. United States, for example, were carried out using Raydist and Decca was used in the speed trials of S.S. Manchester Spinner off the Isle of Man. This paper discusses various methods of determining the ship's speed, the diameter of the turning circle and other data normally measured during sea trials, and makes an assessment of their relative convenience and accuracy.