The effect of systemic mannitol administration on retinal adhesive force in the rabbit was investigated in vivo. The retinal adhesive force, 1 hour after intravenous mannitol injection (2.5 g/kg), was 45% greater than that in control eyes. When adhesiveness had been weakened by injecting Ca(2+)-free edetic acid (EDTA) solution into the subretinal space, intravenous mannitol still enhanced adhesion. Mannitol administration seems to be effective in enhancing retinal adhesion, even under the conditions where it has been weakened by other mechanisms.