In 24 rabbits both eyes were treated in the perilimbic area with hyperthermia by focussed ultrasound at a frequency of 4.65 MHz. The intra-ocular pressure (IOP) decreased significantly in all eyes. The effect of pre-treatment with indomethacin and prednisolone on the inflammatory response induced by the insonification was assessed by determination of protein in the aqueous humour 2 h after ultrasound treatment. Local pre-treatment with indomethacin but not with prednisolone was followed by less increase in protein concentration of the aqueous humour as compared to placebo-treated controls. The IOP was not influenced significantly by the drug pre-treatments.