Heartburn is a common symptom in clinical practice, but as many as 70% of patients have normal findings from upper endoscopy. Most of these patients have nonerosive reflux disease (NERD) or functional esophageal disorders. NERD is the most common phenotype of gastroesophageal reflux disease, and functional heartburn is the most common cause for refractory heartburn. In patients with NERD, symptoms arise from gastroesophageal reflux and esophageal hypersensitivity, whereas in patients with functional heartburn, symptoms result from esophageal hypersensitivity. A diagnosis of NERD requires endoscopy and reflux testing, whereas a diagnosis of functional heartburn also requires esophageal manometry. NERD is treated most commonly with medical, endoscopic, and surgical antireflux approaches, whereas functional heartburn as well as NERD can be treated with neuromodulators, psychological intervention, and complementary medicine options.