Physiotherapists regularly use the hydrotherapy pool for commencing and progressing partial weight-bearing ambulation. By selecting gradually decreasing depths of water in which to walk the patient, the weight which passes through the patient's lower limbs ran he increased in a controlled manner. The only quantitative measurement of percentage weight-bearing to have appeared in the hydrotherapy literature is that of 10%, when the subject is immersed to the level of the neck. A simple experimental method was devised to measure the percentage weight-bearing for several levels of immersion. Eighteen subjects were weighed on dry land and also whilst partially immersed in the hydrotherapy pool and from the results obtained, percentage weight-bearing values were determined. These values will enable physiotherapists to use a more scientific approach to weight-bearing in the pool and to correlate their hydrotherapy treatments with walking re-education on dry land.