Bovine and porcine trabecular cells in Petri dish cultures were exposed to cyclic mechanical stretching of the dish bottom for 30 second cycles (2 Hertz) at a strain magnitude of 4.5 mm/m for up to 3 days. Growth rate of the cells was not affected by the stretching but production of prostaglandin F2 alpha (PGF2 alpha) increased. We believe one stimulus for production of PGF2 alpha in trabecular cells may be the stretching of the trabecular meshwork caused by changes in aqueous flow and intraocular pressure.