Abstract: To clarify the role of adrenal glands in hypertensive animals, levels of catecholamines and corticosteroids in plasma and the mRNA expression of the associated enzymes were measured in 6 and 9-week-old stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar Kyoto rats (WKY) following cold stress. With and without cold stress immersing in cold water at 4°C for 15 sec, catecholamines, adrenocorticotropic hormone (ACTH) and corticosteroids in plasma and mRNA expression in adrenal glands were measured using high performance liquid chromatography (HPLC), enzyme immunoassay (EIA) and DNA microarray, respectively. L-dopa, dopamine and adrenaline in plasma increased more in SHRSP than WKY at 6 and 9 weeks of age after cold stress. Th, Ddc and Dbh mRNAs were upregulated in the adrenal glands of SHRSP after cold stress, more apparent at 6 weeks than at 9 weeks of age. Corticosterone and aldosterone in plasma increased in both SHRSP and WKY, but this effect was more apparent in SHRSP after elevation of ACTH evoked by cold stress. Expressions of cyp11a1 and cyp21a1 mRNAs were upregulated in both SHRSP and WKY at 6 weeks of age after cold stress. We conclude that l-dopa, dopamine, and adrenaline were synthesized following induction of Th, Ddc and Dbh mRNAs. Corticosterone and aldosterone in plasma increased following the induction of cyp11a1 and cyp21a1 mRNAs which are stimulated along with ACTH elevation following cold stress in young SHRSP more than WKY. This difference may be related to the initiation and/or development of hypertension in SHRSP in normal condition and/or during stress.