AbstractTwo cholinesterase reactivators (K074 and K075) were synthesized and their reactivation efficacy against tabun‐inhibited acetylcholinesterase of the rat brain was tested in vitro. Comparing this efficacy showed that commonly used oximes (pralidoxim, obidoxime and HI‐6) were practically without reactivation potency. On the other hand, oximes K074, K075 and trimedoxime were satisfactorily effective. Moreover, K‐oximes reactivated tabun‐inhibited AChE at lower concentration (10−4 and 10−3 m) in comparison with trimedoxime (10−3 and 10−2 m). Thus, K‐oximes can be considered as the most effective reactivators of tabun‐inhibited AChE at present. Copyright © 2005 John Wiley & Sons, Ltd.