Partial vitrectomies were performed in rabbits, replacing 40% of initial vitreous volume with 100% sulfur hexafluoride, and concentrations of sodium, potassium, calcium, magnesium, ascorbate, and protein were determined in aqueous and vitreous at 10, 14, 21, 28, 56, and 110 days. There were significant increases of potassium, calcium, magnesium, and protein above control values at varying times throughout the study. Vitreous potassium concentration was decreased at 14 and 21 days. All other measurements were similar to control values. Results of studies indicate that, following vitrectomy in rabbits, the blood-retinal barrier can re-form in 14 days and blood-aqueous barrier in ten days. However, a greater than normal exchange diffusion of these measured substances occurs between aqueous and vitreous through 21 days. Four eyes with cataracts, vitreous membranes, and/or detached retinas demonstrated elevated aqueous and vitreous protein concentrations through 110 days, although other measurements returned to normal levels.