The kinetics of the anti-DNP antibody response to DNP-pneumococcus appearing in tears and bile (IgA) and serum (IgM and IgG) was examined in rats after the application of antigen either via the ocular-topical (OT) or gastrointestinal (GI) routes. It was found that IgA responses were obtained each time in tears after either OT or GI antigen doses given monthly for three months, but that the OT route gave rise to consistently higher tear antibody titres than the GI route of immunization. Comparable IgA responses were found in bile using either route. In serum a small primary IgM response was consistently obtained but the main antibody found was IgG, the timing and degree of response being about the same for both routes. When the adjuvants Avridine in liposomes or MTP-PE were added along with the antigen it was found that with either immunization route, the tear IgA response was much reduced compared to when no adjuvant was used; the serum IgG response was marginally increased when adjuvant was added. The effects of binding anti-DNP monoclonal IgA or IgG1 to antigen before immunizing via the OT route was also studied. It was found that the presence of immunoglobulin of either isotype in the complex caused an increase in the serum IgG response, but that the tear IgA response was diminished in rats receiving IgA/antigen complexes compared with those receiving IgG/antigen or antigen alone.