The selective precipitation of α-lactalbumin (α-La) is the basis for one of the possible methods in whey protein fractionation. Calcium concentration, type of acid added and pH play important roles in α-La precipitation and on the following resolubilisation. Two washing steps are enough for quantitative removal of β-lactoglobulin entrapped in the precipitate. α-La losses are minimised during washing steps (5%) when NaCl is used as washing agent. The most important parameter to control during the resolubilisation step is pH, the maximum amount of the initial re-dissolved α-La being 76% when the pH is adjusted to 7.5, CaCl2 concentration is 0.2 m and prior precipitation is carried out adding citric acid. Addition of CaCl2 is not necessary to dissolve α-La because of the fact that there is enough calcium in the precipitate to join all α-La; however, its presence improves the solubilisation yield (66% vs. 75%).