This paper details the design and implementation of a robust H/sub /spl infin// controller designed to stabilise the roll motion of a ship. The paper outlines the design of a classical PID controller in order that comparisons may be made between the performance of the two methods. The paper gives a brief background to the main theoretical aspects of H/sub /spl infin// control before introducing the actual H/sub /spl infin// controller design methodology. Having discussed the design process, the paper then leads on to the description of the actual sea trials evaluation of the H/sub /spl infin// controller. These trials took place onboard the MV Barfleur during its crossings of the English Channel during the 21st-25th November 1995. The results of these trials are then be analysed and the appropriate conclusions drawn.