Clinical confusion and inappropriate management continues to surround endometriosis. It is poorly recognized that the disorder can exist in two different morphological forms that have different symptoms, signs and prognosis. Earlier classification systems have been useful for research but are of limited value in aiding day-to-day management. In the clinic, two discrete phenotypes can be defined by the presence or absence of palpable nodules in the deep pelvis. Patients with such nodules with or without associated ovarian endometrioma usually have severe symptoms with significant risks of bowel and urinary tract involvement. The predominant histological feature of these lesions is extensive fibromuscular hyperplasia (adenomyoma). These patients will often need extensive surgical intervention. Patients without such palpable lesions usually have the classic superficial subperitoneal lesions with endometrial-like glands and stroma on histological examination. This group often has less severe symptoms and has little risk of developing serious associated problems. These lesions may be helped by medications and/or simple ablative surgery. It is suggested that these collections of symptoms and signs or syndromes be named after the pioneers who first described the lesions. Cullen's syndrome can be used to describe those patients with severe symptoms of endometriosis associated with palpable pelvic nodules. Sampson's syndrome can describe those with similar symptoms associated with a structurally normal pelvis.