Plasma catecholamines and their metabolites were sampled in 13 medication-free patients with obsessive-compulsive disorder (OCD) and 29 normal controls. In addition to severe OCD symptoms, the patients had significantly higher anxiety, tension, and resting pulse rates than the controls. Nonetheless, mean plasma concentrations of norepinephrine (NE) and epinephrine (E), the catecholamine metabolites 3-methoxy-4-hydroxyphenylglycol (MHPG) and homovanillic acid (HVA), and the stress-related hormone cortisol did not differ between OCD patients and normal controls. When the patients and control populations were combined and average plasma NE and E levels calculated over 35 min, subjects with a higher mean NE output (greater than 1.1 pm/ml) had higher Profile of Mood States depression scores than subjects with a low NE output (less than 1.1 pm/ml). Altogether, these results indicate that elevated plasma catecholamine measures are not likely to be associated with the pathophysiology of OCD.