Appendicitis is a common cause of abdominal pain for which prompt diagnosis is rewarded by a marked decrease in morbidity and mortality. The history and physical examination are at least as accurate as any laboratory modality in diagnosing or excluding appendicitis. Those signs and symptoms most helpful in diagnosing or excluding appendicitis are reviewed. The presence of a positive psoas sign, fever, or migratory pain to the right lower quadrant suggests an increased likelihood of appendicitis. Conversely, the presence of vomiting before pain makes appendicitis unlikely. The lack of the classic migration of pain, right lower quadrant pain, guarding, or fever makes appendicitis less likely. This article reviews the literature evaluating the operating characteristics of the most useful elements of the history and physical examination for the diagnosis of appendicitis.