Abstract: This invention relates to a process for selectively separating the alpha-lactalbumin from the proteins of whey; the process comprises a heat treatment of the whey previously concentrated to a dry matter content of 10 to 40% by weight, and acidified to a pH of less than 4, preferably from 3 to 3.5, said heat treatment being carried out at a temperature not exceeding 75.degree. C., preferably from 45.degree. to 75.degree. C., for a duration of 15 seconds to 1 hour so as selectively to precipitate the alpha-lactalbumin; this heat treatment is followed by the recovery of the alpha-lactalbumin in the form of a precipitate and possibly of the other lacto-proteins remaining in solution in the residual whey. The process presents the advantage of being simple to carry out and being of low cost.