During a 5 month, double blind crossover study of the clinical effect of cyclobenzaprine on 7 patients with fibrositis, weekly measurements were done of plasma beta-endorphin (endorphin, prostaglandin E (PGE) and catecholamines). Endorphin levels were normal but varied with tender point tenderness. Mean plasma dopamine and PGE were elevated. Norepinephrine was normal to very high while epinephrine levels were continuously low to normal. We conclude that patients with fibrositis have a neurotransmitter plasma profile like other chronic pain states having stress and increased vasomotor activity with the possible exception of having low circulating epinephrine. This disparity may mark a failure of central nervous system pain modulation in fibrositis.