Uterine fibroids are benign (noncancerous) tumors of the uterus (womb) that occur in about 66% of women by the time they reach the age of 50. Fibroids are tumors of the smooth muscle cells of the uterus. The collagen content of the tumor gives it a hard, fibrous texture, thus the name fibroid. These tumors are also called leiomyomata or myomas. The cause of uterine fibroids is unknown. There is a familial predisposition, with a 2- to 3-fold increased risk if a mother or sister is affected. African American women are 3 times more likely to be affected than other women. In African American women these tumors can occur at an earlier age and are often larger and more symptomatic. In some women fibroids do not cause symptoms and do not require any treatment. In many women fibroids cause abnormal uterine bleeding and pelvic discomfort. The January 7, 2009, issue of JAMA includes an article about a woman with uterine fibroids.