Vitrectomy and the subsequent vitreous fluid exchange alter the chemical and physical properties of the vitreous. This study assessed the time course alterations of total protein, ascorbic acid and lactic acid in the rabbit vitreous cavity following vitrectomy. Normal values were 2.2 ± 1.2 mg/ml, 8.5 ± 1.0 mg/l00 ml and 16.8 ± 3.5 μmol/ml, respectively. Nine groups of 5–10 adult albino rabbits underwent closed vitrectomy using physiologic saline, Ringer’s lactate and BSS plus solutions. Samples were withdrawn at 3 and 24 h and 7 days after vitrectomy. Total protein levels increased in all groups at 3 and 24 h (20-30 mg/ml). Ascorbic acid measurements at 24 h rose only with saline and BSS plus. At 24 h the BSS plus group was the only one demonstrating an increased lactic acid concentration.