The purpose of this study was to compare the AmniSure rapid immunoassay with standard methods for diagnosing rupture of fetal membranes. Patients presenting with signs/symptoms of membrane rupture between 15 and 42 weeks of gestation were invited to participate. Standard/control methods were performed to establish a diagnosis and compare it with AmniSure results. AmniSure performance metrics and their 95% confidence intervals were calculated. A total of 203 patients agreed to participate. Discrepancies between the control method and AmniSure were noted in seven cases. In these cases, true positives and negatives were determined by retesting with the control method and AmniSure and by noting sonographic evidence of low amniotic fluid. In the final analysis, the AmniSure diagnostic test demonstrated a sensitivity of 98.9%, specificity of 100%, positive predictive value of 100%, and a negative predictive value of 99.1%. AmniSure is highly accurate in diagnosing fetal membrane rupture.