The purpose of this clinical study is to determine, in a controlled fashion, the ability of a topical formulation of Nitroglycerin, MQX-503, to improve the patient's health assessment as indicated by patient and physician assessments, decrease the frequency of Raynaud's events, decrease the duration of Raynaud's events, and decrease the symptoms (pain, tingling, numbness) in the fingers of Raynaud's patients. The study will include patients with moderate to severe primary Raynaud's Phenomenon (RP) and with moderate to severe Raynaud's Phenomenon secondary to autoimmune diseases, such as scleroderma.