Vanadate is a potent inhibitor of calcium stimulated ATPase, Na, K-ATPase, and may have adrenergic activity. Using the iontophoresis method, we compared vanadate to a BSS control and the standard iontophoresis model (6-hydroxydopamine/epinephrine) by measuring induced ocular shedding of latent HSV-1 in different host animals. Latent trigeminal ganglionic infections were established in Balb/c mice and New Zealand rabbits following corneal inoculation with HSV-1 [W] strain, and later confirmed by cocultivation. Latently-infected animals (>1 month post-infection) were divided into three treatment groups. Each group was iontophoresed with BSS, vanadate 1% or 6-HD 1%, and then treated topically for 10 days with BSS, vanadate or epinephrine respectively. Reactivation and recovery of latent HSV-1 was detected by daily ocular swabbing, plating, and observing progressive viral growth in Vero cells. The vanadate group had more virus-positive eyes than the BSS control group in mice, (8/32 vs. 1/32 P<.01), and also in rabbits (14/20 vs 6/22 P<.01). Virus-positive animals and total positive swabs were also higher for vanadate than BSS in both mice and rabbits. Furthermore, while vanadate was associated with fewer virus-positive eyes than 6-HD&EPI (8/32 vs. 17/32 P<.02) in mice, there were no significant differences in rabbits. We conclude that vanadate promotes ocular shedding of latent HSV-1, and may act through an adrenergic mechanism.