OBJECTIVE To study the effect of disposable extended-wear soft contact lenses on the corneal epithelium. METHODS Thirteen healthy patients (1 male, 12 females; average age, 26.3 +/- 7.6 years) with or without histories of previous contact lens use were recruited for this study. Specular microscopic pictures of the corneal epithelium and endothelium were taken with the help of a specular contact lens, before and after 3 months of contact lens use. The pictures were analyzed by means of a computer-assisted morphometric analysis system. RESULTS The mean cell area and coefficient of variation (CV) of the mean cell area of the corneal epithelium before contact lens use were 639.4 +/- 84.0 microns 2 and 29.1 +/- 13.2, respectively. After lens wear, the mean cell area increased to 819.7 +/- 99.2 microns 2 (P less than 0.01), whereas the CV decreased to 20.0 +/- 6.1 (P less than 0.05). The corresponding values for the endothelium were 300.8 +/- 22.5 microns 2 and 36.4 +/- 7.3 before contact lens use, and remained at 322.3 +/- 27.8 microns 2 and 32.8 +/- 3.7 after contact lens use, respectively (P greater than 0.05). CONCLUSIONS Based on the 3-month results, disposable extended-wear soft contact lenses caused similar enlargement of the mean cell area of the superficial corneal epithelium, as has been reported previously. It would appear that disposable lenses may cause the same metabolic and physiologic changes in the corneal epithelium as do conventional extended-wear soft contact lenses.