Uterine leiomyomas are a common clinical occurrence for gynecologists. The current approach to treating these neoplasms is shaped by classic surgical principles and the knowledge that these tumors are responsive to the gonadal steroids estrogen and progesterone. As knowledge of leiomyomas advances through the techniques of molecular biology and molecular genetics, new concepts are developed that go beyond just myomas as steroid-responsive tumors. Understanding the molecular events involved in the transformation of a normal myometrial cell into a neoplastic cell and the subsequent growth of these leiomyoma cells will be important in determining the pathogenesis of these tumors and providing new targets for treatment. Knowing the role of peptide growth factors, including basic fibroblast growth factor and transforming growth factor-beta, in the pathogenesis of leiomyoma-related symptoms might lead to new treatments targeting these molecules or their receptors. As the effects of genes, including HMGIC and HMGI(Y), are determined; new treatments to prevent leiomyoma formation or growth may be developed. As we gain understanding of the molecular events that cause benign gynecologic conditions such as leiomyomas, safer and more effective treatments might be found as we enter the 21st century.