Background: Chlamydia trachomatis is one of the most common sexually transmitted bacterial infections and it is a leading cause of female infertility worldwide. Chlamydial infertility is characterized by tubal factor infertility and high titres of serum IgG to C. trachomatis. A successful pregnancy under these conditions could be achieved only through in vitro fertilization (IVF). This project aims to identify serological markers and develop a serological technique that could diagnose C. trachomatis –related infertility with high specificity and sensitivity. It also aims to understand the underlying immunological process that lead to the disease states. Methods: The peptides that are serologically associated with chlamydial tubal infertility were identified through in-silico immunoglobulin epitope screening approach and proteomic-peptide-immunoglobulin pull down strategy. These peptides will be assayed against sera of 120 patients from various defined disease cohorts through an ELISA-based technique. The cut –off value and the diagnostic performance of the assay (specificity and sensitivity) will be determined consequently. Results: Based on our preliminary screening, we found that individual peptides, peptide 11, Peptide 12, Peptide 13A and Peptide 13B, and their combinations were found to have higher IgG serological responses for patients with C. trachomatis-related infertility as compared to acute infections (p<0.05). An ELISA technique based on triple combination of these peptides (peptide 11/ peptide 12/ peptide 13A) showed a significant increase in absorbance values of IgG antibody in chlamydial infertility cohort as compared to acute infection cohort. Differential IgG subclass reactions to these peptides in the infertility cohort compared to acute infection indicate that these peptides are involved in the distinct immunological processes that result in pathology. Significant increase in absorbance values for IgG2 and IgG3 in the infertility cohort was observed for peptide combinations of peptide 11/peptide 13B and peptide11/12 respectively. High levels of IgG3 in patients with chlamydial infertility are consistent with previous findings.