The tear content of antibodies specific for various infectious agents has recently begun to be investigated. Important parameters of tear analysis with respect to antibody content are the method of tear collection and the laboratory techniques used to detect specific antibodies in the lacrimal fluid. Normal tears contain antibodies directed against both bacteria and viruses, and the antibody response in lacrimal fluid during immunization of animals and humans has been studied to some extent. This response has also been analyzed in humans during and after natural infection with certain viral and bacterial pathogens. It has become clear that local antibody synthesis takes place in the lacrimal gland, but at least some of these antibodies appear in tears because of lymphocyte sensitization in the common mucosal immune system. A certain degree of transudation of serum antibodies to tears is also often encountered, especially in severely inflamed eyes. Much of the data currently available needs to be confirmed, and more extensive studies need to be carried out for many pathogens. Potential benefits of such studies include development of new diagnostic techniques as well as a better understanding of when and how antibodies confer protection or may be potentially damaging.