The effect of cold provocation on myocardial perfusion was studied in 21 patients with systemic sclerosis and 8 healthy controls. The cold provocation was designed not to cause a pain reaction, and no rise in heart rate/blood pressure product occurred during provocation. Myocardial perfusion was assessed by measurement of thallium uptake by imaged single photon emission computed tomography. No patient had clinical evidence of cardiac involvement, but abnormal electrocardiographic (ECG) findings were found in 5. In 12 patients cold-induced reversible perfusion defects were found; 9 of these also had permanent defects. A further 3 patients had permanent perfusion defects but no reversible defects. The permanent and/or reversible perfusion defects were not related to age among the patients and were not seen in any of the healthy controls, whose age distribution was similar. The reversible and permanent defects were not related to other features of systemic sclerosis, nor to the ECG findings. It is concluded that abnormalities in myocardial perfusion are common in systemic sclerosis and may be present without apparent clinical myocardial involvement. A cold-induced vasopastic process in the myocardial circulation might contribute to the development of the patchy myocardial fibrosis seen in patients with systemic sclerosis.