Problem-The endocervix is a major target of Chlamydia trachomatis (CT) infection, but little is known about the immune repertoire in this tissue, or its response to these common bacteria.Method of Study-Using a cytobrush, we isolated cells from the endocervix of 20 women during CT infection, and post-antibiotic treatment. Endocervical swabs and blood were taken in parallel. Endocervical cells were enumerated, and endocervical and blood T cells immunophenotyped. CT was genotyped by sequence analysis of the OmpA gene, and quantified by culture.Results-CT genotypes were D, E, F and Ia, and infectious burden varied considerably. Endocervical T cell and neutrophil numbers were highly elevated during infection, with both CD4 and CD8 T cell subsets accumulating. Regardless of the presence or absence of infection, the endocervical cell infiltrate was dominated by effector memory T cells, and the numbers of CCR5 and CD103 expressing T cells was significantly higher than in the blood. HLA-DR expression by endocervical T cells was significantly increased during infection.Conclusions-The human endocervix exhibits a distinct cellular response to C.trachomatis infection that can be longitudinally evaluated by cytobrush sampling. Infecting organisms can be sampled and analyzed in parallel.