Chorioamnionitis is a serious complication during labor at term and is associated with adverse neonatal outcome affecting approximately 10% of pregnancies. It is diagnosed clinically or microbiologically or by histopathologic examination of the placenta and umbilical cord. The clinical criteria for chorioamnionitis found in preterm or term women include maternal fever combined with 2 or more findings of maternal tachycardia, fetal tachycardia, leukocytosis, uterine tenderness, and/or malodorous amniotic fluid. These subjective findings are neither sensitive nor specific. However, clinical chorioamnionitis requires a high index of suspicion, timely diagnosis, prompt antibiotic treatment, and delivery, which may help reduce the potentially devastating outcome of maternal and neonatal infections. This article focuses on clinical chorioamnionitis and presents the physiologic immune response during pregnancy, the definition of chorioamnionitis, clinical diagnostic criteria, and implications for practice.