Tackykinins are involved in the inflammatory process of a large number of diseases. The role of the tachykinins in ischemic brain injury was evaluated by the serum levels of Substance P (SP), one of the most known tachykinins and detected by a competitive enzyme immunoassay. The study was performed in 15 human females and 3 human males with typical manifestation of complete stroke (12 cases) or transient ischemic attack (6 cases). The mean SP level in the serum of patients with transient ischemic attack (0.53+/-0.25 ng/ml) and of patients with complete stroke (0.31+/-0.14 ng/ml), showed significantly higher values than in controls (0.10+/-0.02 ng/ml). Moreover, in transient ischemic attack, the SP values were significantly higher than in cerebral complete stroke. But SP levels, based on the timings of classification of patients (i.e. before 12 hours: 0.34+/-0.15 ng/ml vs. 12 to 24 hours: 0.26+/-0.11 ng/ml) with brain injury, did not show any significant difference. Both values anyway were significantly higher than in controls. Our original results demonstrate the SP increase during cerebral ischemia. Further studies are necessary to verify if SP has an effective physiopathological role in the neurological ischemic damage, or if it is only a concomitant phenomenon. Our data, if confirmed, will be particularly important, not only to improve the knowledge of cerebral ischemic injury, but also for diagnosis and therapeutic approaches.