Histological and bacteriological findings in comparison to clinical data concerning intubation for 38 dead premature infants and newborns were studied to elucidate conditions complicating intratrachial intubation at the laryngeal level. The larynx was intact in 3 cases. Slight lesions of mucosa (epithelabrasion, hemorrhage) were found in 13, moderately severe lesions (necrosis of epithelium, ulcers, pseudomembranes) in 11, and severe lesions (deep necrosis, perichondritis with sceletisation) in 10 cases. 1 case showed a stage of regeneration. The narrow passage between the two processus vocales is a site of predilection for tubus-induced lesions, the epithelium bein immediately adjacent to the cartilage. Successful bacteriological demonstration of the infectious agent correlated with the rising degree of mucosal lesions, and increasing duration of intubation. 3 cases, however, already had severe lesions after short-time-intubation. Formal and causal pathogenesis are described. Essential causes are: trauma of intubation, irritation by the tubus in situ, duration of intubation, and infection. Regenerative power of the infantile laryngeal mucosa is strong. Permanent lesions may occur as scarred stenosis. Careful indication, accurate and careful technology of intubation, choice of the smallest possible diameter of tubus, good care for the tubus, and generous prophylaxis against infections are to be demanded.