The diagnosis of abdominal pain is difficult. It requires additional skills and care when the patient is an adolescent. Although the approach required to diagnose a specific disease entity known to be causing the pain symptom is easy, the decisions to take when the patient has the complaint without specific signposts pointing to one entity or another is difficult. In the acute presentation, the decision as to which tests to order or which therapies to initiate must be made almost totally on presenting symptoms and signs. Often the definitive test necessary for the differential (eg, urine culture, cervical culture for gonococcus) will not be reported by the time a clinical decision must be made. In the recurrent presentation, more time is available, but the yield from invasive and expensive tests is lower and more difficult to justify. There are no data prospectively collected in a representative sample of adolescents presenting with abdominal pain in whom a systematic approach to diagnosis was utilized. Thus the relative likelihood of finding urinary tract infection or pelvic inflammatory disease accounting for the symptom, or the relative usefulness of a barium enema examination vs laparoscopy for evaluation of right lower quadrant pain is unknown. As a result, emphasis in this description has been placed on presenting symptoms and signs. Recognizing that diagnostic clinical judgment often involves "pattern recognition," typical presentations have been stressed. However, it should be apparent that this will be insufficient to guarantee diagnostic accuracy. Two of the main reasons for this are the similarity of presentation of so many entities, and the prevalence of atypical presentations. However, a number of principles can be recommended (Table 2): (1) adolescents have different presentations than do younger children; (2) contrary to common belief, adolescents have different presentations than do adults; (3) be aware of increasing prevalence in adolescents of entities that cause abdominal pain at all ages; (4) be aware of entities relating to the genitourinary tract entering into the differential diagnosis; (5) be aware of entities related to life-style changes and exposure to environmental precipitants; (6) appropriate evaluation of the problem of abdominal pain includes assessment of the symptom, the anxiety secondary to the symptorm, and the dysfunction secondary to the symptom; (7) history taking requires excellent communication to overcome shyness relating to patient's self-awareness of sexuality or outright denial of the symptom's significance; (8) appropriate evaluation most often includes a sensitive, expertly performed pelvic examination by an experienced examiner (Cowell) (9) in acute pain presentations, clinical judgment requires consideration of the potential negative consequences of missed "surgical" abdomen, and surgical/gynecologic consultation is often indicated; (10) in recurrent pain presentations, evaluations other than base line tests (history, physical, and pelvic examinations, blood count, ESR, urinalysis, and culture) should not be "shotgun" but used selectively and staged according to relative likelihood of the entity being sought, and usefulness of the procedure in detecting it. Enrollment of the patient as a "coinvestigator" and use of a diary has been found to be helpful in detecting patterns and focusing secondary anxiety about the symptom. It has been estimated that well over 100 entities may present as abdominal pain. Many common (eg, stool retention, gastroenteritis, Mittelschmerz) and less common (eg, abdominal tumors, endometriosis) entities that enter the differential diagnosis agnosis have not been discussed. In the face of these possibilities, I usually adopt the following strategy: (1) with acute pain presentations, to consider first entities with potentically severe consequences requiring early definitive treatment (eg, appendicitis, ectopic pregnancy, ovarian torsion, pelvic inflammatory disease) and to move "down" the differential only when there is good evidence that these first entities are not implicated; and (2) with recurrent presentations, to consider first entities that are most common (eg, nonspecific recurrent abdominal pain, irritable bowel syndrome) and to move "up" the differential to further investigation only when there is good evidence implicating other specific entities. However, no strategy will be appropriate for all situations, and we are far from having a successful recipe for diagnostic success with abdominal pain in adolescents.