The laser Doppler flowmeter, an instrument highly sensitive to changes in blood flow velocity in the dermal microvascular bed, was used to examine a sympathetic vasomotor response (SVR) in 40 patients with lateral epicondylitis. There was a significant association between the absence of a normal SVR in the skin overlying the affected enthesis compared with the unaffected contralateral epicondyle (P < 0.01). These results suggest that local dysfunction of the sympathetic nervous system may be associated with the pathogenesis of anatomically discrete pain in the enthesopathy of epicondylitis.