Women in labor who receive epidural analgesia are more likely to experience hyperthermia and overt clinical fever. The gradual development of modest hyperthermia observed in laboring women with epidural analgesia is not seen in those electing other forms of analgesia or unmedicated labor. Clinical fever is also far more likely in women laboring with epidural analgesia. It is possible that the observed slow increase in mean temperature is an artifact of averaging the temperature curves of a small group of women who eventually develop fever with a larger group who remain afebrile throughout labor. Selection bias confounds the association between epidural analgesia and fever, because women at risk for fever-due to longer duration of ruptured membranes, longer labor, more frequent cervical examinations, and other interventions-are also more likely to select epidural analgesia. However, even randomized trials have confirmed a higher incidence of fever in epidural-exposed women, suggesting a causal relationship. The mechanisms of epidural-associated fever remain incompletely understood. Altered thermoregulation and an antipyretic effect of opioids given to women without epidural analgesia may explain part of the phenomenon, but the most likely etiology is inflammation, most commonly in the placenta and membranes (chorioamnionitis). The consequences of maternal fever are diverse. Obstetricians are more likely to intervene surgically in laboring women with fever, and neonatologists are more likely to evaluate neonates of febrile women for sepsis. More ominously, maternal inflammatory fever is associated with neonatal brain injury, manifest as cerebral palsy, encephalopathy, and learning deficits in later childhood. At present, there are no safe and effective means to inhibit epidural-associated fever. Future research should define the etiology of this fever and search for safe and effective interventions to prevent it and to inhibit its potential adverse effects on the neonatal brain.