Calcinosis cutis is a frequent, difficult to treat manifestation of systemic sclerosis (SSc) associated with high morbidity. The aim of this prospective, controlled, monocentric study was to assess safety and efficacy of extracorporeal shock wave therapy (ESWT) for calcinosis cutis of the finger in SSc patients.A 12-week proof of concept study in which 4 SSc patients with calcinosis cutis were treated at one painful finger with high-energy, focused ESWT, in 3 sessions with one-week interval between each session. A second, untreated finger, served as control. The outcome parameters were: change in pain, change in size of calcification measured by ultrasound (US) and computed tomography (CT) and of the force by pressing the finger against a Dolorimeter.Pain was reduced (by 91% and 60%) in the treated finger in two out of four patients. There was no change in the control fingers. The size of the calcinosis in the treated finger was reduced in three (US) and four patients (CT). Inter-assessor agreement was acceptable for US volume measures (ICC=0.863).We could show promising evidence for safety and efficacy of ESWT for chronic, treatment resistant calcinosis cutis in SSc patients, thus justifying the initiation of larger multicentre controlled trials.