SummaryIn the course of this study, authors searched out the pronostical signification of different elements.They came out to following conclusions. First of all, the suppuration of the lung is a very serious illness, which considerateli in its whole, is burden with mortality of about 65 %.If some pronostic should be established, one should state exactly the anatomical form, and should be looking if he is in presence of acollectedordiffusedsuppuration. In the first case, of a well bounded abscess, the pronostic is good, as about 80 % of ill people recover spontaneously.In the second case, it is very bad, as the proportion of death is of 80 %. This being acquired, neither the age (excepted above 70 years) neither the sex, neither the localisation (as far as it should not be plainly cortical) nor the previous state of the lung (excepted preexisting bronchectasis) do not seem to influence the evolution of the illness. The nature of germs founded in the sputum can not serve as a base to establish a pronostic. The hemoptysis seems to be an unfavourable sign, the vomic is without signification.The laboratory findings are of no help, as the sedimentation or the hematologic exams do not bring decisive dates. Only eosinophily seems to be of a favourable pronostic.Establishing a daily graphic of sputum and temperature, it could be possible to follow gradually the evolution of the illness.As long as the expectorated volumes can be put down in a triangle, as the authors call«a triangle of security»which fixes the duration of suppuration, the illness will have many chances to cure. The suppuration which evolves unfavourably does not possess this caracteristic.The authors give a very great practical importance at this dates.