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Acute puerperal metritis (APM) in dairy cows is a common disease occurring in the first 10 d after calving. According to a widely accepted definition, the diagnosis is primarily based on body temperature and sensorial assessment of vaginal discharge. The scope of this study was to evaluate the reliability for color, smell, and viscosity of vaginal discharge from healthy cows and cows with APM. Fifteen investigators evaluated 6 vaginal discharge samples 10 times. Subsequently, the investigators rated the health status of the cows and the diagnostic value of color, smell, and viscosity. In a final questionnaire, the investigators estimated their ability to diagnose APM correctly and the influence of experience. Reliability was tested using Cohen's kappa (κ). Our study revealed slight to moderate reliabilities concerning the assessment of vaginal discharge. Overall interobserver reliability for color, smell, and viscosity was κ=0.15, 0.27, and 0.44, respectively. Overall intraobserver reliability for color, smell, and viscosity was κ=0.35, 0.39, and 0.6, respectively. By means of a questionnaire, overall personal expertise to detect cows suffering from APM correctly as such was estimated to be 59%, whereas the diagnostic value of a combination of color, smell, and viscosity to detect cows with APM correctly was estimated to be 91.1% perfect. We found a discrepancy between reliability and the personal perception of diagnostic value. Our study shows that the sensorial assessment of color, smell, and viscosity of vaginal discharge in cows postpartum is subjective.