Abstract: The invention concerns a process for pretreatment of cellulosic chip-formed raw material by impregnation. In the process, first a vacuum treatment is carried out without preceding moistening treatment, and as soon as possible after the vacuum treatment penetration is carried out with a solution of chemicals or with water at the atmospheric or a higher solution pressure. In this way the fiber cavities can be filled optimally, which promotes a uniform and adequate diffusion of the solution into the fiber walls significantly. The process can be carried out, e.g., in a device which comprises a tank (11) for the treatment of the raw material and therein a feed opening (18) for the solution as well as an opening (14) for removal of the raw material, which said opening (14) communicates preferably with a reception tank, wherein the atmospheric or a higher pressure prevails.