Mild acute pancreatitis has a low mortality rate, but patients with severe acute pancreatitis are more likely to develop complications and have a much higher death rate. Although serum amylase and lipase levels remain the most widely used diagnostic assays for acute pancreatitis, other biomarkers and inflammatory mediators such as trypsinogens are being investigated for clinical use. Ranson's criteria, the Imrie scoring system, the Acute Physiology and Chronic Health Evaluation (APACHE II) scale, and the Computed Tomography Severity Index are systems for classifying severity of this disease; the Atlanta classification is widely used to compare these systems and standardize clinical trials. New developments in imaging modalities such as endoscopic ultrasonography and magnetic resonance cholangiopancreatography increase the options available to physicians for determining the cause of pancreatitis and assessing for complications. Enteral nutrition is preferred to parental nutrition for improving patient outcomes. Clinical trials are ongoing to evaluate the role, selection, and timing of antibiotics in patients with infected necrosis.