We applied the tandem scanning confocal microscope (TSCM) to 30 healthy human corneas of 3 normal volunteers and 27 patients with cataract and retinal detachment to observe normal corneal epithelial cells in vivo. All corneas were normal under slit lamp microscopic examination. The superficial and basal epithelial cells close to the basal lamina in the central cornea were recorded on videotape and analyzed by a computer-assisted digitizer. The mean cell areas of superficial cells exposed at the surface and basal cells at the horizontal section were 624 +/- 109 microns2 and 66 +/- 5 microns2, respectively. The ratio of superficial to basal mean cell area was 11.0 +/- 4.5. TSCM was thus useful in evaluating the relationship between superficial and basal cells in human corneal epithelium in vivo.