Three methods of taking samples of bronchopulmonary secretions; transtracheal aspiration (TT), sputum collection, and fibro-aspiration, were compared in 43 patients with severe pneumopathies. There was no significant difference in the number of times a pure or dominant germ was isolated by using the three procedures in these 43 cases. In contrast, however, there was a significantly lower number of polymorphous flora and more sterile samples observed when using TT than with the other two methods. When antibiotics are given 1 to 7 days before taking the samples, there is a significant reduction in the number of cultures having a germ in the pure state.