Raynaud's phenomenon is usually a benign acrosyndrome which few of the currently available therapies improve significantly. This makes the evaluation of the efficacy of vasodilators very difficult, especially as there are no standardised complementary investigations to quantify their effects. Assessment is based essentially on careful interrogation and the use of an analogical scale remains the method of reference. The multiplicity of factors inducing the acrosyndrome necessitates cross-over trials versus placebo over sufficiently long periods of observation (if possible, one month). As regards follow-up and objective evaluation, reactivity to cold is a promising method providing the tests can be standardised with respect to methodology and expression of results.