Cod liver oil administered intramuscularly (0.2 ml/day) lowered intraocular pressure (IOP) of the rabbit from 21 mmHg to 18 +/- 0.4 mmHg (p less than 0.05 n = 8). A higher dose of cod liver oil (1 ml) further lowered intraocular pressure to 14.5 +/- 0.3 mmHg which remained at this level for up to 80 days when the rabbits were sacrificed. Intramuscular injections of liquid lard did not alter IOP in rabbits. When treatment with cod liver oil was stopped, IOP rose to baseline levels. Topical treatment with cyclooxygenase inhibitors had no effect on the IOP lowering effect of cod liver oil. Topical treatment of rabbit eyes with 1% aspirin solution twice daily (up to 28 days) and flurbiprofen t.i.d. (up to 15 days) caused no alteration in the decrease in IOP seen with intramuscular cod liver oil treatment for up to 28 and 15 days respectively.