Dysmenorrhea, or menstrual pain, is the most common menstrual symptom among adolescent girls and young women. Most adolescents experiencing dysmenorrhea have primary dysmenorrhea, defined as painful menstruation in the absence of pelvic pathology. When the patient's history suggests primary dysmenorrhea, empiric treatment should be initiated. When a patient does not experience clinical improvement for her dysmenorrhea within 3-6 months of therapy initiation, her obstetrician-gynecologist should investigate for possible secondary causes and for treatment adherence. Secondary dysmenorrhea refers to painful menses due to pelvic pathology or a recognized medical condition. Endometriosis is the leading cause of secondary dysmenorrhea in adolescents. Endometriosis should be considered in patients with persistent, clinically significant dysmenorrhea despite treatment with hormonal agents and nonsteroidal antiinflammatory drugs, particularly if no other etiology for chronic pelvic pain or secondary dysmenorrhea has been identified based on history, physical examination, and pelvic ultrasonography. The appearance of endometriosis may be different in an adolescent than in an adult woman. In adolescents, endometriotic lesions are typically clear or red and can be difficult to identify for gynecologists unfamiliar with endometriosis in adolescents. Endometriosis in adolescents is considered a chronic disease with potential for progression if left untreated. The goals of therapy include symptom relief, suppression of disease progression, and protection of future fertility. Therapy must be individualized, and obstetrician-gynecologists should consider patient choice, the need for contraception, contraindications to hormone use, and potential adverse effects and counsel the adolescent and her family on treatment options.