Mumps is a systemic viral illness, preventable by vaccination, that typically affects children and is characterized by unilateral or bilateral swelling of the parotid glands. Uncommon complications such as orchitis, oophoritis, deafness, pancreatitis, aseptic meningitis, and encephalitis occur more often in adults. Recent outbreaks of the disease appear to be caused by a failure to maintain herd immunity in certain populations, particularly in affluent white communities. This article reviews the clinical manifestations, diagnosis, and potential complications in patients with mumps.