Background:Midazolam is a frequently used benzodiazepine in anaesthesiology and intensive care. Aim: The aim of pilot study was to monitor its eff ect during heart perfusion in the laboratory rat. Methods: The same groups of animals (n = 10). The 1 st group was treated with midazolam in a dose of 0.5mg/kg i.p. The 2 nd group was a placebo. After i.p. administration of heparine injection of 500 IU dose, the hearts were excised and perfused (modifi ed Langendorf's method). Working schedule: stabilization/ischaemia/reperfusion proceed at intervals of 20/30/60 min. Monitored parameters in isolated heart: left ventricle pressure (LVP), end-diastolic pressure (LVEDP), contractility (+dP/dt max ).Results: The treated hearts showed improved postischemic recovery, reaching LVP values of 92 ± 6 % at the end of the reperfusion, placebo only 61 ± 7 %. In placebo hearts LVEDP rose from 10.0 ± 0.5 mmHg to 43 ± 4 mmHg after, in treated animals only about 25 mmHg. The treated hearts improved +dP/dt max recovery during reperfusion to 91 ± 8 %. These values were signifi cantly greater than those obtained from the placebo hearts.Conclusions: Positive changes in monitored parameters were found in this experimental pilot study. We conclude that the administration of midazolam in laboratory rats has a cardioprotective potential against ischemia-reperfusion induced injury.