Described was a case of massive (right upper and middle lobe and basal segments of the left lower lobe) clinically atypical pneumonia, «rapidly» resolving during treatment with beta-lactam antibiotics, but complicated by acute respiratory distress syndrome, acute respiratory failure, infectious and toxic shock, cerebral and pulmonary edema that led to a lethal outcome. No macroscopic pathological signs of pneumonia were found, histologically in one of the sections of the lower lobe of right lung in the alveoli some serous-leukocyte exudate was found. The paradox of the situation (pneumonia almost resolved, but the patient died) became the reason to conduct a retrospective analysis, which showed that over the preceding 10 years, there were 27 cases of progressive pneumonia (3.1% of 873 cases of pneumonia), usually atypical during treatment with beta-lactam antibiotics, four of which, including the described one, had a fatal outcome caused by acute respiratory distress syndrome. The remaining patients in whom beta-lactam antibiotics were changed to macrolides, recovered. This suggests the ability of beta-lactam antibiotics to participate in the pathogenesis of acute respiratory distress syndrome, or even be its cause.