100 ml water-loading per kilogram body weight in rabbits increased the intraocular pressure significantly. Under these conditions there was also a decrease in ocular rigidity resulting in lower measurements of intraocular pressure and this in turn could be responsible for too high an estimate of the outflow resistance using indentation methods. Pilocarpine 4% did not lower the intraocular pressure significantly in the water-loading test in rabbits. The water-loading test does not seem suitable for evaluation of all types of drugs with potential hypotensive effects.