The induction of experimental subarachnoidal hemorrhage (ESH) in the dog results in a rise in the adrenaline plasma concentration. The changes in plasma noradrenaline are biphasic: an ‘early noradrenaline gap’ during the first 2 min is followed by a ‘late noradrenaline peak’. It is likely that adrenaline is chiefly concerned with the systemic reactions occurring after ESH, although it can have additional effects at the myocardial level. There is a nonlinear relation between catecholamine concentration changes in tissue and plasma and the myocardial reaction to ESH. This can be explained by the complex interaction of the different factors regulating the level of the catecholamines in blood and tissues.