The 16 papers in the 2004 edition of the annual review focus on theories for understanding the motion of waves and new medical applications. The opening chapter chronicles early work published in Europe on the theory of water waves. Other topics include coating flows, Langmuir circulation, shock wave drag reduction, modeling of accidental explosions, turbulent flows over rough walls, biofluid mechanics in flexible tubes, ray models for internal waves, and experimental and computational methods for quantifying blood flow velocity and pressure.