Objective: To determine the reproducibility of the postcoital test among trained observers. Methods: Twenty-eight infertile patients presenting to the Brigham and Women's Hospital over a 1-year period were recruited for the study. After a standardized collection of specimens for the postcoital test, four fellowship-trained reproductive endocrinologists evaluated six postcoital test characteristics and gave their overall impression of the test. Each observer was blinded to the patients' identities and clinical histories as well as to the ratings of the other observers. The six characteristics included an assessment of the cervical mucus by ferning, cellularity, spinnbarkeit, and consistency, and of sperm by total count per high power field and percent motility. Scoring was adapted from World Health Organization (WHO) criteria for semen-cervical mucus interaction. Statistical analysis included the kappa statistic to determine agreement among observers for postcoital test characteristics and the Mantel-Haenszel test to determine the association between overall impression and the other test characteristics. Results: Agreement among the four observers was best for sperm number and motility (39% of cases) and worst for cellularity, spinnbarkeit, and overall test impression (11, 14, and 14% of cases, respectively). The kappa statistic ranged from a low of 0.13 for cellularity, demonstrating poor reliability (95% confidence interval [CI] 0.03–0.23), to a high of 0.51 for sperm number, demonstrating fair reliability (95% CI 0.41–0.60). Only sperm number and percent motility were significantly associated with the overall impression (P < .001). Conclusions: In a blinded study, the characteristics of the postcoital test were found to have poor to fair reproducibility among trained observers using a standardized WHO scoring system. The observers' overall impressions of test quality correlated with sperm number and motility only. We question the validity of the postcoital test as a diagnostic tool in the evaluation of infertility.