The authors attempted to demonstrate the latency of herpes simplex virus type 1 (HSV-1) in corneas obtained during penetrating keratoplasty from patients with herpetic stromal keratitis in the nonactive (subsided) stage. The subjects comprised 20 patients (9 men, 11 women; average age 43.5 years). Infectious virus was not detected in the supernatants following corneal homogenization and centrifugation. Latent virus was detected in the cultured supernatants of the corneal sections from 8 patients. Although the ganglion trigger theory by Hill et al is conventionally supported as the mechanism of recurrence of herpetic keratitis, the present results suggest a ganglion and skin trigger theory, in which proliferation from latent HSV-1 in the cornea (peripheral tissue) might stimulate the ganglion.