Both carpal tunnel syndrome and Raynaud's phenomonon are common conditions in the general population. These two different conditions frequently cause similar symptoms such as tingling, numbness, and "deadness of the fingers". They may also co-exist for instance in scleroderma or rheumatoid arthritis. In order to study the association, if any, between these two conditions, we studied 93 patients with idiopathic carpal tunnel syndrome confirmed in electro-physiological tests with 57 control subjects, for the presence of Raynaud's phenomenon by means of a previously validated questionnaire. Raynaud's phenomenon was detected significantly more frequently (P = 0.002) in patients with idiopathic carpal tunnel syndrome (36%) compared to control subjects (12%). Thus there appears to be an association between these two conditions. The mechanism for this is not clear. Sympathetic dysfunction may play a part. Practitioners should be aware of the similarity of the symptoms and the possibility that the two conditions may co-exist.