A modified, bilateral iontophoresis technique was used to evaluate herpes simplex virus (HSV) reactivation and epinephrine distribution and concentration in full-thickness corneas and in trigeminal ganglia of rabbits. Infectious virus was recovered from 58% of epinephrine-induced eyes 24-96 hours after iontophoresis. A histochemical adrenochrome oxidation method localized epinephrine exclusively in the corneal epithelium and anterior stromal lamellae after iontophoresis. Epinephrine introduced iontophoretically into the corneal epithelium and stroma did not reach the ganglion level as detected by the assay. Radiometric-enzymatic assay of corneal and ganglionic tissues demonstrated a transient increase in total corneal catecholamine levels from an average of 417 ug to an average of 778 ug; concentrations returned to approximate control values 24 hours after iontophoresis. Ganglion total catecholamine levels increased from an average of 606 ug to an average of 1211 ug for a 12-hour period and remained elevated at 24 hours after iontophoresis. Epinephrine acting directly on the corneal epithelium and epinephrine metabolites at the ganglion level could act synergistically to induce ocular and ganglionic HSV reactivation.