In today's practice, the medical aerosols are most often composed of soluble and hygroscopic particles emitted by the evaporation of a primary aerosol of solution droplets. The instruments on the one hand and the formula of the aerosoltherapeutical solution on the other should be worked out so that the fixation of aerosol in the lung be most efficient. The main data in view of this improvement are studied: --the curve of fixation of aerosols of sodium chloride in lung and the recall of the standard curve for insoluble and inert particles; --the characteristics of medical aerosol devices subjected to approbation or still unregulated (spray can). The calculation of the doses determined in standard conditions are illustrated together with the parameters which can make them vary.