CONTEXT: Fibroids occur in 20-40% of women of reproductive age and progesterone plays a role in stimulation their growth. OBJECTIVES: To investigate the modification on uterine and fibroids volume, to study Doppler changes in uterine arteries and in fibroid supplying vessels and to assess possible symptomatic relief after 3 months treatment with UPA. METHODS: Patients were evaluated clinically for the symptoms complained and underwent ultrasound examination before and after 3 months therapy with UPA. PATIENTS 42 premenopausal women with symptomatic fibroids were enrolled in the study INTERVENTIONS Uterine volume and uterine arteries pulsatility index (PI) and resistance index (RI) were assessed for each patient. Considering that some patients had more than one fibroid, vascularization (supplying vessel PI and RI), localization and size of a total of 73 fibroids were also recorded. MAIN OUTCOME MEASURES The percentage of uterine volume reduction after therapy was 14% (p=0,03) while the percentage of fibroid volume reduction was 32,8% (p= 0,01) with a significant decrease of all fibroids vascular indices. Dividing fibroids depending on their localization according to FIGO classification, type 5 resulted to have a higher volume reduction (39%) comparing to other fibroid types (p=0,03). RESULTS: After 3 months of UPA patients had a significant improvement of symptoms with a reduction in uterine bleeding, pelvic pain, bulge-like syndrome and urinary and intestinal symptoms (p < 0,05). The uterine volume and the fibroids dimension as well as fibroids vascularization decreased significantly after therapy. CONCLUSION: Fibroid treatment by UPA therapy results in a significant improvement of fibroid-related symptoms; moreover it proved to be effective in decreasing both uterine and fibroid volumes and fibroid vascularization. Type 5 fibroids seem to have the major response to treatment.