Background: Alström syndrome (AS) is a rare autosomal recessive condition characterized by retinal degeneration, childhood obesity, and severe insulin resistance. Dilated cardiomyopathy of unknown aetiology is a well-recognized and potentially lethal complication. The aim of this study was to investigate the relationship between vascular function, hyperinsulinaemia and cardiac performance in AS. Materials and methods: Fifteen subjects with AS (mean age 21 years, range 10-35) were studied and compared with age-, sex-, and blood pressure-matched healthy controls. Large artery stiffness and wave reflections were assessed in both groups by measuring aortic and brachial pulse wave velocity (PWV) (carotid-femoral and carotid-radial) and augmentation index (AIX) (Sphygmocor). In AS subjects, left ventricular function was assessed by echocardiography and metabolic parameters including fasting insulin, glucose, lipids and brain natriuretic peptide were also measured. Results: Comparing AS subjects vs. controls (mean ± SD), AIX was elevated in AS subjects (18 ± 9% vs. 3 ± 11%, P < 0·0001). No significant changes in brachial PWV (8·1 ± 1·3 m s-1 vs. 7·3 ± 1·1 m s-1, P = 0·14) or aortic PWV (6·5 ± 1·1 m s-1 vs. 6·0 ± 1·0 m s-1, P = 0·26) were observed. AS subjects were hyperinsulinaemic and had disturbances in lipid profiles relative to controls. No correlations were observed between vascular, metabolic and echocardiographic parameters. Conclusions: In AS there are alterations in the shape of the central arterial pressure waveform associated with augmented aortic systolic pressure and indicative of increased wave reflection. Unfavourable central arterial haemodynamics in AS may contribute to the development of cardiomyopathy but other aetiological factors are probably involved.