Tear lysozyme and .gamma. A globulin (Ig[immunoglobulin]A) concentrations were determined [in man] during a 24 h period using a simple quantitative method. Tear lysozyme was significantly elevated between 9-12 a.m., and reduced during sleep periods from midnight to 3 a.m. Tear IgA concentrations showed individual variability, but no discernible diurnal rhythm.