Coating and fibre impregnation are studied from the theory of Landau and Levich (Acta Physicochem. USSR 17 (1942) 42), Deryagin (Acta Physicochem USSR 39 (1943) 13) and more recent approaches of De Ryck and Quere (J. Fluid Mech 311 (1996) 219) and Rebouillat et al. (2000). Chemical and physical effects as well as hydrodynamic influence the impregnation. To study fibre impregnation at speeds higher than 2 m s(-1), a high-speed impregnation unit was developed to reach fibre velocities of 5 m, s(-1) and above. The wettability and the hydrodynamic phenomena associated with impregnation at high fibre velocity have been investigated on mono- and multi-filaments yam structures passing through a bath of liquid. The negligibility of gravity in comparison with inertia at high velocities has been experimentally observed by studying the effect of fibre inclination on the fluid thickness and by processing dimensional analysis. Moreover, the impregnation phenomena have been studied owing to a new image analysis set-up, which allows to measure directly the fluid thickness on fibres and to study the dynamic meniscus region, which has been successfully modelled to allow back calculations under specific conditions.