In this study, correlation between duration of premature rupture of the membranes (PROM) and the degree of membrane, decidua, and myometrium infections were histologically investigated. The study was carried on 61 women with term pregnancy (30 with PROM, 31 control group). During cesarean section, a full-thickness biopsy specimen of the uterine wall from serosa to decidua was obtained with scissors. Chorioamnionitis was histopathologically identified by neutrophilic leukocyte (NL) infiltration of the membranes. Endometritis or myometritis were diagnosed when the acute inflammatory process extended to the decidua or the myometrium successively. It was found that the presence and depth of NL infiltration significantly correlates with the interval between rupture of membranes and termination of pregnancy. © 1998 Wiley-Liss, Inc.