A kit using mouse monoclonal antibody against human alpha-fetoprotein (anti-AFP kit) has been developed. Cervical secretion (n = 34) and vaginal fluid (n = 15) was obtained from 30 pregnant volunteers. All 31 specimens obtained from women with intact membranes tested negative while all 18 specimens from women with premature rupture of membranes (PROM) tested positive. The newly developed kit allowed rapid and accurate diagnosis. We compared the kit results with those obtained by pH determination (nitrazine, bromthymol blue test) and measurement of AFP concentrations by enzyme-linked immunoassay (EIA).