Following application of 2N sodium hydroxide, or 8.1N ammonium hydroxide to rabbit cornea, the aqueous humor pH reached a maximum of 10.2, 11.9, and 12 within six minutes following 20-, 50-, and 100-mu1 sodium hydroxide burns, respectively; after two hours the pH had fallen to 8.5, 10, and 10.5. The maximum rise following application of 100-mu1 of ammonium hydroxide was 10.8, declining to about 9 at two hours. The fall in pH following a 100-mu1 sodium hydroxide burn was not greatly influence by external lavage. However, the pH was significantly lowered (12 to 10) by paracentesis alone and further reduced by immediate or delayed intracameral administration of phosphate buffer. On the basis of these results moderately severe and severe alkali burns of the eye should be treated by paracentesis and if possible with anterior chamber reformation with a sterile solution.