This study recorded the effects on ocular pressure of drinking a half liter of water in 5 min. Of the 324 subjects, treated or nontreated, presenting an ocular pressure greater than 18, the results after 15 min were as follows: a pressure rise between 3 and 4 points in 28.5% of the cases; a rise of between 5 and 6 points in 13.5% of the cases and, in 8% of the cases, a rise of more than 6 points. These figures were approximately the same for all ages and, to a lesser degree, for subjects at risk with normal ocular pressures. This transitory variation in pressure which recurs with the ingestion of liquids during meals might play an aggravating role in cases of glaucoma-induced nerve head ischemia with or without high ocular pressure.