Proscar is prescribed to help shrink an enlarged prostate. The prostate, a chestnut-shaped gland present in males, produces a liquid that forms part of the semen. This gland completely encloses the upper part of the urethra, the tube through which urine flows out of the bladder. Many men over age 50 suffer from a benign (noncancerous) enlargement of the prostate. The enlarged gland squeezes the urethra, obstructing the normal flow of urine. Resulting problems may include difficulty in starting urination, weak flow of urine, and the need to urinate urgently or frequently. Sometimes surgical removal of the prostate is necessary. By shrinking the enlarged prostate, Proscar may alleviate the various associated urinary problems, making surgery unnecessary.

You can find an extensive list of recent scientific research abstracts about PROSCAR here

Adv Ther. 2002 Nov-Dec;19(6):297-306
Long-term clinical and biologic effects of the lipidosterolic extract of Serenoa repens in patients with symptomatic benign prostatic hyperplasia.
Pytel YA, Vinarov A, Lopatkin N, Sivkov A, Gorilovsky L, Raynaud JP.
Scientific Research Institute of Urology, Moscow, Russia.

Permixon, the lipidosterolic extract of Serenoa repens, is widely used for the treatment of symptoms associated with benign prostatic hyperplasia (BPH). This open study assessed the efficacy and tolerability of Permixon 160 mg twice daily administered for 2 years. One hundred fifty-five men with clinically diagnosed BPH and complaints of prostatic symptoms were enrolled in the study. At 6, 12, 18, and 24 months, the International Prostate Symptom Score (I-PSS), quality of life, and sexual function score were recorded, and urodynamics and biologic values were measured. Adverse events were recorded every 3 months. I-PSS and quality of life improved significantly from baseline at each evaluation time point. At the end of the study and at each evaluation, maximum urinary flow also improved significantly. Prostate size decreased. Sexual function remained stable during the first year of treatment and significantly improved (P = .001) during the second year. Prostate-specific antigen was not affected, and no changes in plasma hormone levels were observed. Nine patients reported 10 adverse events, none related to treatment. Improvements in efficacy parameters began at 6 months and were maintained up to 24 months. These data demonstrate the long-term efficacy and tolerability of Permixon and support its use as a first-line medical therapy for uncomplicated symptomatic BPH.

Horm Res. 2002;58 Suppl 3:43-8
Flavonoid and botanical approaches to prostate health.
Katz AE.
Center for Holistic Urology, New York Presbyterian Hospital, and Columbia University School of Medicine, College of Physicians and Surgeons, New York, NY, USA.

Benign prostatic hyperplasia (BPH) is a common problem among aging men that produces significant morbidity and health care costs. Contention exists as to whether currently available surgical and pharmacologic options for BPH are appropriate for men in the watchful-waiting stage. Recently, the possible benefits of phytotherapies (plant-derived preparations) in treating BPH and prostate cancer are being considered. Several phytotherapies, including saw palmetto, Pygeum africanum, curbicin, and isoflavone-containing supplements (red clover [Trifoleum pratense] and soy), are widely used in patients with BPH. Evidence suggests that the consumption of isoflavones found in legumes is related to lower rates of BPH and prostate cancer among Asian men. When evaluating natural therapies, the physician should look for a product that relieves symptoms and is safe, contains a health-conferring ingredient with a defined mechanism of action, and is standardized for that ingredient. Phytotherapies, particularly isoflavone-containing supplements, are likely to have an important role in the management of patients in the watchful-waiting stage of BPH.