Serum erythropoietin (EPO) levels are partially controlled by the sympathetic outflow to the kidney. We have studied whether patients with multiple system atrophy (MSA), known to be associated with dysautonomia, are EPO-deficient. Eighteen MSA patients were studied along with 32 idiopathic Parkinson's disease (PD) patients, 23 controls with iron-deficiency anaemia, and 18 healthy individuals. Serum creatinine was normal in all groups. Mean haemoglobin (Hb) concentration in MSA patients was 13.7 ± 1.7 g/dL. Four MSA patients had unexplained anaemia (minimum Hb: 10.5 g/dL) and abnormal autonomic function tests including significant postural hypotension, whereas none of the PD patients was anaemic. Serum EPO levels were suppressed in relation to anaemia in MSA patients compared to elevated EPO levels in iron-deficiency anaemia patients (difference of regression lines P < 0.001), indicating EPO deficiency in the anaemic MSA patients. Serum EPO levels in PD patients were within normal range. A subset of MSA patients has anaemia and postural hypotension, which may be associated with EPO deficiency. This may have therapeutic implications. © 2001 Movement Disorder Society.