Customer expectations are increasing, especially with regard to the individualization of products, in which additive manufacturing is described as a disruptive technology. With a view to using the technology in a series application, extensive knowledge of the starting material, the powder, is necessary. In this article, AlSi10Mg in powder form (grain size range: 15–70 µm), which is used for the selective laser melting process, is analysed on the basis of various investigations. A distinction is made from other researchers, as a total of six powders of the same specification but from different manufacturers were used. An investigation of the relative humidity of the powders in the as-delivered condition was carried out using a moisture meter. It could be shown that the moisture lies between 5% and 15% and that the moisture can be reduced by about half by using dry bags. A qualitative examination with a scanning electron microscopy showed that the morphology and size distribution differ. Not only partially round, but also very misshapen particles and particles with and without adhesions are present. The flowability was determined with a calibrated Hall flowmeter. It was found that a lower proportion of fine particles in the powder lead to a more uniform flowability. In the investigation, a distinction was made between powder in the as-received state and dried powder. The particle size distribution was determined with a laser diffraction method and evaluated according to the Mie theory. To be able to carry out porosity analyses on the basis of micrographs, test cubes with the dimensions (10 × 10 × 10 mm3) were used. The parameters scanning speed (400–600 mm/s), hatch spacing (0.19–0.29 mm), and laser power (220–320 W) were varied. The results vary between 0.12% and 5.46% porosity. To combine the results, a pairwise comparison and a use-value analysis were carried out. Overall, the differences in the powders of the different manufacturers were found to be small, so that a recommendation was made for the most economical powder.