We evaluated antibody responses to trachoma vaccine in Taiwan monkeys using the micro-immunofluorescence assay. In the experiment with B/TW-5 gradient and genetron vaccines, the level of antibody titers could be correlated with the vaccine dose administered. Immunotype-specific protection from disease or modification of disease severity was associated with higher homologous antibody titer. In the experiment with A/G17, A/SA-6, and C/TW-3 genetron vaccines, an extraordinary high antibody response was demonstrated. Again, the high homologous antibody titers were associated with complete or partial protection from eye disease caused by the eye challenge inoculations. Cross reactions between immunotype A and C in the micro-IF test were also reflected in the vaccine protection observed in this experiment. It is concluded that there is an excellent correlation between the micro-IF antibody responses, the mouse toxicity prevention test, and vaccine prevention of monkey trachoma eye disease. Study of micro-IF antibody responses should be a useful tool for development of effective trachoma vaccine. * One ml of vaccine with oil adjuvant was given intramuscularly 2 times, one month apart. Ab: Serum antibody titer to challenge type prior to eye inoculations. DS: Ten-week average disease score of the inoculated eye, right with B/TW-1 and left with C/TW-3. * Antibody titers measured prior to challenge. ** Ten-week average disease scores of inoculated eyes, right with A/G-17 and left with C/TW-3.0: no disease, 0.1-3.0: mild disease, and <3.0: severe disease.