1. There is increasing evidence that a substantial number of patients who suffer from angina have normal epicardial arteries (Syndrome X), and it has been suggested that these individuals have a generalized disorder of small vessels not confined to the intramyocardial vasculature. 2. Small arteries were therefore obtained from biopsies of skin and subcutaneous fat from nine normotensive patients with Syndrome X and nine matched control subjects. Vessels were dissected and mounted as ring preparations in a myograph for morphological and functional assessment. 3. Morphological measurements revealed a significant increase in media thickness/lumen diameter ratio in arteries from patients with Syndrome X. Contractile responses to U46619 were similar in arteries from patients and control subjects. Endothelium-dependent relaxation induced with acetylcholine and bradykinin was greater in arteries from patients although differences were not statistically significant. Endothelium-independent relaxation induced by forskolin and sodium nitroprusside was not different. 4. In conclusion, these data demonstrate that subcutaneous small arteries from patients with Syndrome X are characterized by increased media thickness/lumen diameter ratios, although contractile responses were normal. Additionally, endothelium-dependent relaxation was not impaired in arteries from these patients. Thus, no significant functional abnormalities were associated with the observed structural differences.