The efficacy of reactivators 2-PAM, MMB-4, TMB-4, toxogonin and HI-6 has been evaluated using the biochemical cholinesterase method. The method allows rapid in vitro evaluation of the reactivators without being disturbed by excess of the organophosphate or reactivator. The highest reactivation was observed with sarin-inhibited acetylcholinesterase. Substantially lower reactivation was found with the cyclosarin-inhibited enzyme whereas AChE, inhibited by soman and tabun, could not be effectively reactivated under the given conditions (enzyme inhibition for 2 minutes and subsequent treatment with the reactivator).