The purpose was to identify distinct inflammatory markers in endometrial tissues of women with abnormal uterine bleeding (AUB) and Chlamydia trachomatis infection. Archived endometrial specimens from 92 randomly selected premenopausal women with AUB were examined for C. trachomatis using the species-specific monoclonal antibody against major outer membrane protein (MOMP) and for histopathology associated with inflammation. Statistical analyses included single and multiple logistic regression. Diagnostic accuracy was summarized using receiver operating characteristic (ROC) curves. Chlamydia trachomatis was detected in 44 (48%) of 92 AUB specimens. There were statistically significant correlations of positive MOMP with higher counts of plasma cells (P < 0.01), macrophages (P < 0.0001), and lymphocytic foci (P = 0.01). The ROC curve for macrophages was the strongest predictor (area under the curve = 0.82) for C. trachomatis. The prevalence of C. trachomatis in women with AUB is under-estimated. Macrophages appear to be a strong marker for the presence of C. trachomatis in the endometrium.