De Leo V1, La Marca A, Morgante G. Abstract The aim of this study was to evaluate the effects of danazol in reducing the volume of fibromyomas and in the treatment of associated symptoms. Twenty women (34-42 years) with uterine fibromyomas were treated with 400 mg/day of danazol for 4-month periods. The women underwent ultrasound examination to determine their uterine volume at enrollment in the follicular phase and after 2 and 4 months. The examination was repeated by the same sonographer 3 and 6 months after the end of therapy. Blood samples were taken on the same days for LH, FSH, estradiol and progesterone assays. After therapy, fibromyoma volume decreased significantly (p<0.01) by an average of 23.6+/-5%. All patients experienced partial or complete relief of symptoms while using danazol. Three and six months after the end of treatment the fibromyoma volume had only increased slightly with respect to the volume at the end of therapy, but was still lower than the starting volume. The present study shows the efficacy of danazol at a dose of 400 mg/day for 4 months in reducing the volume of fibromyomas and associated symptoms. The mechanism by which danazol reduces the volume of fibromyomas may be due to reduced estrogen concentrations and to its antiprogesterone effects on uterine myomas.