Delta(9)-tetrahydrocannabinol (THC), an active narcotic principle of marijuana, was solubilized and administered intravenously to two male volunteers. Changes in intraocular pressure were recorded and compared to changes in the cortical effects of THC, as indicated by the subjects' report of degree of "high." The peak effect of THC on the central nervous system coincided well with the reduction of intraocular pressure induced by the drug; hypotony, however, outlasted euphoria. The results indicate that THC may have value as a hypotonizing ocular medicant.