Manipulative therapy is a commonly used treatment method in the management of low back pain. The therapy has advantages in being able to direct movement to a particular segment that is painful and lacking normal movement. Many physiotherapists utilize hydrotherapy pools in the treatment of back pain. The main advantages and purported therapeutic effects of immersion in warm water include the enhancement of pain relief and reduction in muscle spasm mediated through the physical and physiological effects of warm water on the body (Skinner & Thomson 1994; Reid Campion 1997; Ruoti et al 1997). The combination of the two therapies would seem to be beneficially complementary and the practice of using manipulative therapy in water is not new. There is some published information on the use of manipulative therapy techniques in water but that which is available, while supporting the principle, also highlights the deficits of the water based medium for the application of manipulative therapy techniques as compared to land based treatment particularly in respect of the localized application of technique. These include the difficulty in gaining fixation of the patient with flotation equipment or pool fixtures and the stability of the physiotherapist in water in performing the technique (Hill 1997). Localizing the line of force of the manipulative therapy technique to a specific joint and controlling the amplitude of the technique are also seen as difficulties (Hill 1997). Investigation of the current descriptions of the application of techniques such as the lumbar postero-anterior mobilization reveal these problems (Skinner & Thomson 1994; Hill 1997). Therefore on first impressions it would seem that the application of small amplitude, localized, passive movement oscillations to a lumbar spinal segment, which are possible in land based treatments, may not be able to be applied effectually in water.