Connective tissue diseases are the most important organic causes of Raynaud's phenomenon, and systemic sclerosis is the most frequent one. Careful history taking and clinical examination eventually lead to further investigations where capillaroscopy and specific autoantibodies tests have the best performances to reach diagnosis. Our understanding of local regulation of blood flow has been improved discovery of new neuromediators and local substances derived from endothelium. These compounds have direct implications for medical therapy and represent new hopes for the treatment of Raynaud's phenomenon which, however, remains difficult and incomplete for most patients.