Background. Vasospasm is one of the underlying causes of morbidity and mortality in subarachnoid haemorrhage (SAH). The therapeutic effects of intracarotid infusion of spermine/nitric oxide complex (SPER/NO) on cerebral vasospasm in an experimental model of SAH were investigated. Method. Twenty-four adult male New Zealand white rabbits (2.6-3.4 kg in weight) were randomly divided into four groups (n = 6), as follows: (I) control group (without SAH and drug), (II) SAH alone group (with SAH, without drug), (III) SAH placebo group (with SAH and saline), and (IV) SAH-SPER/NO group (with SAH and SPER/NO). The fresh autologous non-heparinized blood was injected into the cisterna magna to induce a SAH, after 24 hour SAH, the substance (saline or SPER/NO) was delivered to animals. All rabbits were scarified at 48-hours of induced SAH. The basilar artery with surrounding tissue was removed from the cranium and processed for paraffin embedding. Histopathological and stereological examinations of the basilar artery were done. Findings. In the SPER/NO treated group of rabbits, the histopathological changes were less severe than in the SAH-alone and SAH-placebo groups. Regarding the intracarotid pressure, there was a statistically significant difference between SAH-alone and SAH-SPER/NO groups and also between SAH-SPER/NO and control groups (p < 0.05). The mean cross sectional area of basilar arteries was 0.26 mm2 in the control, whereas in SAH alone, placebo and SAH-SPER/NO groups were 0.13, 0.15 and 0.20 mm2, respectively. Interpretation. It is well known that NO is a critical substance involved in cerebral vascular dynamics. Present results indicate that treatment of vasospasm with SPER/NO in SAH may be promising. However, further studies should be done on this substance to clarify its effect on vasospasm before using the drug in clinical situations.