Classic techniques like videofluoroscopy, stationary manometry, and ambulatory 24 h pH-metry are routinely used in the clinic to study patients with dysphagia, chest pain and reflux-related symptoms. Although these techniques have been very useful over the years, both for diagnosis and for therapeutic guidance, there are still many patients with dysphagia or chest pain who remain undiagnosed even after testing, and patients with typical and atypical symptoms of gastroesophageal reflux disease, with normal pH-metry findings, who do not respond adequately to antisecretory therapy. Esophageal impedance monitoring is a new technique that can be used alone and in combination with pH-metry and manometry to evaluate bolus transport and all types of gastroesophageal reflux (acid and nonacid). This review describes the esophageal impedance monitoring technique and summarizes the published validation studies that compare impedance monitoring with other methods, as well as normal values and reproducibility of impedance patterns and their association with symptoms.