AIM: Botulinum toxin A is an acetylcholine release inhibitor and a neuromuscular blocking agent indicated in adult patients for the temporary improvement in the muscle. The aim of the present study is to investigate the effect of botulinum toxin A on rat aorta contraction. MATERIAL AND METHODS: Descending thoracic aorta was isolated after cervical dislocation from wistar albino rats (n=12). Aorta tissues were cleaned and sectioned into 3-4 mm long rings. Rings were placed in organ baths containing Krebs solution, thermoregulated at 37oC and aerated (95 % O2 and 5% CO2). Changes in isometric tension of aorta rings were recorded using a four channel force displacement transducer. Phenylephrine (PE 10-6M) was applied and contractions were recorded in both groups. 100 units vacuum-dried powder Botulinum Toxin Type A (Botox) was diluted by 5ml 0.9% NaCl solution. Botox doses of o.1mL (4 units), 0.2 mL (8 units) and 0.3 mL (12 units) were added in organ baths and contractions were recorded. RESULTS AND CONCLUSIONS: After 0.3 mL of botox was given, significant inhibition of spontaneous contractions was noticed (p<0.05). Vasodilatation of aorta suggests that botox may have beneficial effects on treatment of peripheral arterial diseases and hypertensive disorders. Further studies are needed to clarify the mechanism of Botulinum Toxin Type A.