In matched specimens of tears and serum from trachoma patients, antibodies were measured against six TRIC antigens. Antibodies were found in the serum of 78% and in the tears of 59% of Tunisian children aged 6 to 9, suffering from severe trachoma. Serum or tear antibodies were found in only 6% of Navajo Indian children aged 7 to 12 with mild trachoma. Although 48% of Navajo students aged 13 to 20 with mild trachoma had antibodies in serum, antibodies in tears were exceedingly rare. Of Samoan adults living in San Francisco, with moderately severe trachoma, 86% had antibodies in serum and 29% in tears. The antibodies in tears were usually of lower titer than in serum, showed similar reactivity with specific TRIC antigens, and seemed to parallel the degree of clinical activity. Most antibodies in tears appeared to be derived from serum, and not to be produced locally.