A wide variety of infectious agents has been associated with acute pancreatitis. Strict diagnostic criteria were developed to assess the relationship between individual microorganisms and acute pancreatitis. Pathologic or radiologic evidence of pancreatitis associated with well-documented infection was noted with viruses (mumps, coxsackie, hepatitis B, cytomegalovirus, varicella-zoster virus, herpes simplex virus), bacteria (Myco-plasma, Legionella, Leptospira, Salmonella), fungi (Aspergillus), and parasites (Toxoplasma, Cryptosporidium, Ascaris). Clues to the infectious nature of pancreatitis lay in the characteristic signs and symptoms associated with the particular infectious agent. How often these agents are responsible for idiopathic pancreatitis is unclear.