The article presents main results of the open randomized investigation of the effectiveness and safety of the new non-depolarizing myorelaxant Nimbex included in the composition of anesthesiological maintenance of thoracal operations of high risk. The authors give data of its influence on neuromuscular conduction and main hemodynamic indices during different periods of the operative intervention. The assessment of the intubation condition, depth of the neuromuscular block and of the dynamics of reestablishment of the neuromuscular conduction is shown. A conclusion is made of the possibility to use the myorelaxant in question as a preparation of choice for the maintenance of thoracal operations in high risk patients.