In subgroups of patients with localised musculoskeletal pain spread of pain and signs of altered somatosensory processing at painful sites, both focal and referred areas have been reported. The purpose of the study was to examine somatosensory processing in patients with mainly unilateral long-term (> or =1 year) trapezius myalgia with ongoing pain for the last 3 months in the trapezius muscle in conjunction with ongoing or recurrent referral of pain to the ipsilateral arm. Ten patients with trapezius myalgia and 10 age- and sex-matched healthy controls participated. Pressure pain sensitivity, low threshold mechanoreceptive function and thermal sensitivity, including thermal pain, were assessed at the site overlying the most painful part of the trapezius muscle and in an area of pain referral in the ipsilateral upper arm/forearm as well as in the corresponding contralateral areas. No significant difference in sensibility was found in the most affected trapezius muscle and contralaterally compared to the corresponding areas in controls. In the area of pain referral there was a significantly increased sensitivity to pressure pain compared to the homologous contralateral area (p<0.01) as well as to the corresponding area in controls (p<0.009). Compared to controls a bilaterally decreased sensitivity to light touch was found in patients in the area of referred pain (p<0.01). No differences were found in the outcome of thermal testing. These findings suggest altered central processing of somatosensory input from the area of referred pain in patients with trapezius myalgia.