Biopsy specimens were taken from the upper tarsal conjunctiva of eight asymptomatic contact lens wearers and quantitative histology was determined and compared to histology from 15 normals and 55 patients with contact lens-induced giant papillary conjunctivitis. No abnormalities were detected in the asymptomatic contact lens wearers. One or more of the three tissue characteristics of giant papillary conjunctivitis--(1) mast cells in the epithelium, (2) eosinophils in epithelium or substantia propria, and (3) basophils in epithelium or substantia propria--was found in all patients with this syndrome, but none was present in any of the eight asymptomatic lens wearers. Trauma occurring over months or even years does not induce histologic alteration in the upper tarsal conjunctiva; the surface changes seen previously by scanning electron microscopy in asymptomatic lens wearers are secondary to trauma, not early aspects of the giant papillary conjunctivitis syndrome.