Systemic toxicity of local anesthetics results from excessive plasma concentrations of these drugs, most often from accidental intravascular injection. Systemic reactions primarily involve the CNS and the cardiovascular system. In general, the CNS is more susceptible to the actions of systemic local anesthetics than the cardiovascular system is, and thus the dose or blood level of local anesthetic required to produce CNS toxicity is usually lower than that resulting in circulatory collapse[1]. Here we present the case of a 45-year-old male patient who had ultrasonography guided supra-clavicular brachial plexus block. The patient had an episode of seizure immediately (with-in 30 sec) after administering the local anesthetic (13 ml given in 5 ml aliquots injected after negative aspiration). He was treated with intravenous midazolam (2 mg stat) and supplemental oxygen via facemask. He had no neurological symptoms afterwards. All laboratory tests and radiological investigations were normal. This case report records the occurrence of local anesthetic toxicity observed as seizure activity, after ultrasound guided brachial plexus block due to accidental intravascular injection, as negative aspiration of the syringe does not always exclude intravascular placement.