Systemic absorption of glucagon from eye drops containing an emulsant caused an elevation in blood D-glucose concentrations in anesthetized rats. Glucagon (0.03 mg) delivered to the eye in buffered saline had no significant hyperglycemic action. However, delivery of glucagon in eye drops containing 0.25% saponin caused a rapid, dose-dependent increase in blood D-glucose values. Maximal absorption was observed 20 minutes after eye drop administration and values returned to baseline after 60 minutes. Immunoreactive glucagon levels measured 20 minutes after administration of eye drops containing saponin plus glucagon were increased by 2.4-fold compared to basal values. Glucagon administration via eye drops was ineffective when 0.5% Brij78 or BL-9 was substituted for saponin. These results demonstrate that in the rat, systemic absorption of glucagon delivered in eye drops is possible, but the choice of an emulsant may be critical.