Research on the use of L-arginine for specific conditions shows:

Angina. Studies suggest that L-arginine might decrease symptoms and improve quality of life in people with a mild to severe form of this type of chest pain.
High blood pressure (hypertension). Some research has shown that oral L-arginine can lower blood pressure in healthy people, people with mild blood pressure elevation and diabetes, and in people with a type of high blood pressure that affects the arteries in the lungs and the right side of the heart (pulmonary hypertension). Infusions of L-arginine also appear to lower blood pressure in people with hypertension.
High blood pressure during pregnancy. Some studies show that L-arginine infusions may lower blood pressure in pregnant women who develop high blood pressure.
Preeclampsia. L-arginine infusions may lower blood pressure in women with this pregnancy complication. Some research shows that taking oral L-arginine might help prevent preeclampsia in pregnant women.
Erectile dysfunction. Taking oral L-arginine might improve sexual function in men with erectile dysfunction due to a physical cause.
Peripheral arterial disease (PAD). When taken orally or by infusion for a short period of time, L-arginine may improve symptoms and blood flow in people with this circulatory condition.