A hydraulic seal is defined between a rotating member such as a turbocharger shaft and a stationary member such as part of a bearing housing of a turbocharger. The members define a projecting annular disc that is received in an annular channel that is filled with hydraulic sealing fluid such as oil. Rotation of the rotary member applies a centrifugal force to the fluid thereby ensuring that it is retained in the channel between walls thereof and the disc. This annulus of fluid provides a hydraulic seal around the shaft between the bearing housing and the compressor or turbine housing. The oil is delivered into the channel from a supply in the rotary member. One of the walls of the channel serves as a weir whereby when the channel has an excess supply of oil is overflows the wall and passes the drain. The arrangement provides an effective seal against blow-by across the turbine end seal and restricts gas flow from the relatively high pressure regions of the compressor and turbine housings into the relatively low pressure area of the bearing housing. It also ensures that there is a continuous flow of oil across the seal so as to prevent it degrading in the high temperature environment.