AIM The aim of the present study was to compare the efficacy of placental alpha-microglobulin-1 (PAMG-1) rapid immunoassay with conventional standard methods for the diagnosis of rupture of membranes (ROM). MATERIAL AND METHODS A prospective observational study was performed in patients with symptoms or signs of premature rupture of membranes (PROM) at the Department of Obstetrics and Gynecology, Faculty of Medicine, Chulalongkorn University. Conventional standard methods were performed to establish the diagnosis and were compared with PAMG-1 immunoassay results. ROM was diagnosed if visualization of fluid leaking from the cervical os or two of the following three conditions were present: positive nitrazine test, ferning test, and nile blue test. The diagnosis of ROM was confirmed by reviewing the medical records after delivery. RESULTS One hundred patients (gestational age 36.5±3.5weeks, range 22-41weeks of gestation) were recruited into the study. Seventy-six percent were preterm and 24% were at term. PAMG-1 immunoassay had a sensitivity of 97.2%, specificity of 69%, positive predictive value (PPV) of 90.8%, negative predictive value (NPV) of 90.9% and an accuracy of 89%. In contrast, conventional combined standard methods had a sensitivity of 88.7%, specificity of 96.6%, PPV of 98.4%, NPV of 77.8%, and accuracy of 91% for the diagnosis of ROM. CONCLUSION PAMG-1 immunoassay is a rapid method for the diagnosis of ROM. PAMG-1 has a higher sensitivity than conventional standard methods for the diagnosis of ROM.