Systemic sclerosis is a multi system disorder, for which there is no satisfactory treatment. Theoretically, dietary supplementation with essential fatty acids may lead to an increase in their derivatives, the vasoactive prostaglandins, which benefit the acute and chronic ischaemic lesions of this disease. We assessed the value of concentrated essential fatty acids in patients with systemic sclerosis, concentrating particularly on vascular symptoms and objective tests of vascular reactivity. Twenty-five patients with systemic sclerosis were randomised to receive concentrated essential fatty acids or placebo, for 6 months in a double-blind parallel group study. There was no significant difference between the active and placebo groups in terms of maximum blood flow after warming, minimum blood flow after cooling or the recovery time after cooling. There were no significant differences between the groups in the other parameters measured. Dietary essential fatty acids have no role in the treatment of vascular symptoms in established systemic sclerosis.