Immunoglobulin concentrations in human tears were determined in 165 patients with different eye diseases by a standard radial immunodiffusion method. IgA was present in all the samples in measurable quantity. The mean IgA values were significantly higher than the controls in patients with acute bacterial conjunctivitis, keratomalacia, corneal graft reaction, blepharoconjunctivitis, and acute keratoconjunctivitis. The values in the patients with vernal conjunctivitis, phlyctenular conjunctivitis, acute bacterial corneal ulcer, and acute endogenous uveitis were not significantly different from those in the controls. IgG could be detected in the majority of the samples but it was in measurable quantity in 18 samples. IgM could be detected in fewer samples. IgD was not detected in any of them. The study indicates that, whenever the immunoglobulin levels in tears are altered in diseased eyes, it is the IgA level that is predominantly altered and not the IgG level.