Broad-spectrum reactivator is an oxime which is able to reactivate acetylcholinesterase (AChE) inhibited by many kinds of organophosphate inhibitors of AChE, mainly nerve agents. There are many AChE reactivators (oximes) as suitable candidates for the broad-spectrum reactivator. Among them, oxime HI-6 is considered as number one, and due to its properties, it is recommended by many armies to be introduced as universal antidotal mean. In this study, we wanted to summarize that the designation “broad spectrum” is prerogative. For this purpose, in vivo evaluation of therapeutical dose of HI-6 (39.0 mg/kg) was performed. Soman, cyclosarin and tabun were used as the typical members of nerve agent family. According to the obtained results, oxime HI-6 did not sufficiently reactivate tabun-inhibited AChE. Brain AChE was also only partially protected. Based on these results, it seems that HI-6 in therapeutical dose has effect only in peripheral compartment.