The absorption of a vasoconstrictive substance labeled with 14C, after application as eye-drops, was studied in animal experiments. After iatrogenous obstruction of the lacrimal punctum with tissue adhesive, a maximum of 6% of the substance could be measured in the total blood volume after an exposure time of 60 min. High relative concentration of the drug could be found in cornea, conjunctiva, and iris, while the concentration in lens, vitreous body, and the rest of the eye was low. The results represent the maximum values of resorption. Additional studies, made by 99mTc-pertechnetate microscintigraphy of the lacrimal drainage apparatus of the rabbit were also performed. The transport of an eye-drop from cornea and conjunctiva to the nasal cavum was found to be very rapid. Therefore it seems to be of little value to carry out investigations on the absorption of eye-drops over long time periods without prior occlusion of the lacrimal punctum.