Equine endometritis is a prevalent and costly disease. It is ranked one of the three most common problems encountered in equine practice. Endometritis can be a frustrating disease for the equine practitioner to diagnose, especially when clinical signs are subtle. The low sensitivity of uterine culture and cytology are hallmarks of the disease. Additionally, chronic inflammation and fibrosis can only be diagnosed through an endometrial biopsy. One limitation is the long turnaround time to get the histological diagnosis, and it is not normally desirable to take an endometrial biopsy in same estrous cycle that the mare is bred. So, a faster noninvasive screening test that can discern mares with subclinical or chronic endometritis is of value for the equine industry. Therefore, our broad objective is to investigate the utility of the endometrial swab and cytobrush to screen mares for endometritis. Estrous mares at the Cornell Equine Park (CEP) and at the Rood and Riddle Equine Hospital will be evaluated and sampled. Each mare will have an endometrial swab and cytobrush, followed by a low-volume uterine lavage (LVL) with 250 mL of saline, and finally a biopsy. Mares will be divided into three groups: 1) CONTROL/HEALTHY; 2) ACUTE; and 3) CHRONIC based on the degree of inflammation on endometrial cytology and/or biopsy and a positive/negative culture. Assays for inflammatory markers will be performed using established and validated fluorescent-bead based multiplex assays in collaboration with the Wagner Lab. Specific aims include: 1) to compare the following markers of inflammation: IL-4, IFN-γ, IL-17A, IL-10, sCD14, IL-1β, TNF-α, CCL2, CCL3, CCL5, and CCL11 in the endometrial swab, cytobrush and LVL fluid of HEALTHY mares, mares with ACUTE and CHRONIC endometritis; and 2) to compare the levels of the inflammatory markers with the degree of neutrophils on cytology/biopsy, with positive cultures and pregnancy outcomes. We anticipate that CHRONIC mares will have increased levels of IFN-γ, IL-17A, TNF-α and CCL2 compared to HEALTHY group, and and that there will be differences in which biomarkers are increased in between the ACUTE and CHRONIC groups. Additionally, the cytobrush and swab will have higher concentrations of the inflammatory markers compared to LVL with more pronounced differences and additional markers detected as the LVL will have a dilution effect. This research will provide more insight into the molecular regulation of endometrial inflammatory response and will provide a fast, non-invasive, and sensitive diagnostic screening tool for equine practitioners.