Anticonvulsant and antilethal effects of imidazenil, a new imidazobenzodiazepine derivative, in fluostigmine (DFP; diisopropyl phosphorofluoridate) intoxications were studied and compared with the effects of diazepam on mice and rats. Special attention was payed to the myorelaxant effects of both drugs. It was stated that imidazenil (i) significantly decreased convulsion intensity in mice, (ii) quickly inhibited seizure patterns in bioelectrical activity in the rat's brain, (iii) significantly increased antilethal effectiveness of the standard therapy in mice intoxicated with DFP. These effects are comparable to those of diazepam. However, effects of imidazenil in the rota-rod test of the mouse were noted in doses 5-10 times higher than therapeutic ones, when effects of diazepam on motor co-ordination were seen in therapeutic dosage.