The congenital pain insensitivity syndrome is accompanied by: a) the presence of a yellow-brown pigment in the basal layer of the epidermis with the histochemical properties of melanin, b) decrease of urinary and blood concentration of dopamine and norepinephrine, c) excretion of melanin and of an abnormal as yet unidentified phenolic metabolite, d) increase in urinary p-hydroxyphenyllactic acid, p-hydroxyphenylacetic acid, indole acetic acid, and e) a high homovanillic acid/vanillylmandelic acid (HVA/VMA) ratio. In this report we show that analgesic patients differ from controls by: a) an increase in norepinephrine excretion after L-tyrosine administration, and b) an increase in norepinephrine, dopamine, DOPA + DOPAC excretion after L-DOPA administration. The administration of L-DOPA eliminates the difference in HVA/VMA ratio between patients and controls. Serum and platelet monoamine oxidase, dopamine beta-hydroxylase and catechol-O-methyltransferase are normal and urinary excretion of biopterins, morphine-like compounds and endorphins is also within the normal range. The comparison of catecholamine metabolism in patients with phenylketonuria, Lesh-Nyham syndrome, congenital sensory neuropathy with anhydrosis and familial dysautonomia on the basis of our data and those in the literature suggests that patients with congenital pain insensitivity display abnormal catecholamine metabolism.