Analysis of incidence and morphology of Klebsiella pneumonia nowadays in the adults (10 observations), children (5 observations) and newborns (23 observations) is presented. The pneumonias account for 11.3% of total number of lobar pneumonias in the adults dying in 1979-1989. Klebsiella infection represent 16.1% of total number of autopsies a year according to the pediatric infection pathology department. Etiological role of Klebsiella is established in 21.5% of total number of autopsies of newborns for 1985-1988, pneumonia being 61% of total Klebsiella infections. Klebsiella pneumonias in the adults correspond in principle to the Friedländer's pneumonia studied in detail by V.D. Zinserling (1891-1960) and his students. Generalized forms of, as a rule, hospital Klebsiellosis with most grave lung damage, unknown up to now, are frequently observed in children. Klebsiellosis was combined practically in all cases both in the adults and children with other bacterial, viral and fungal infections. The degree of clinico-morphological manifestations may considerably vary.