Baclofen (sold under the name Baclosan((C)), Lioresal((C))) is a muscle relaxant. This drug is chemically different from other muscle relaxants. Due to its pronounced psychotropic effect the drug is often a subject of abuse especially among young people. The article deals with the dynamics of lung histopathology in acute baclofen poisoning. Experimental studies were performed on 15 Wistar rats. The animals were divided into 3 groups (the controls and two experimental groups). The controls included 5 intact rats. Each experimental group included 5 animals. Both groups were treated with baclofen at a dosage of 85 mg/kg. The duration of the experiment was 3 and 24 hours, respectively. We revealed a complex of pathological changes in the lungs of the rats. There were circulatory disorders in all the elements of the microcirculatory bed, areas of emphysema, atelectasis and dystelectasis, WBC infiltration of intralveolar septa and their thickening due to edema. The changes were even more severe 24 hours after the drug administration. These results along with the results of chemical analysis will be useful in establishing the fact of baclofen intoxication and the exact moment of the intoxication.