A simple method for the determination of human corneal epithelial permeability to fluorescein is presented. The method consists of applying a 1% sodium fluorescein solution to the cornea for 8 minutes by means of an eye bath, rinsing the eye, and measuring corneal fluorescence by fluorophotometry. The permeability value is calculated from the corneal fluorescein concentration immediately after the bathing period. Mean permeability value determined in 86 eyes of 46 volunteers aged 15 to 67 years (mean 30.9 years) was 0.038 nm/s +/- 0.017 SD. No significant correlation with age was found (corr. coeff. = 0.17, P = 0.28). The reproducibility was within 10%.