A one-step crystallization process was developed for production of edible grade a-lactose monohydrate from ultrafiltered sweet cheese whey permeate at room temperature. Concentration of permeate to 30% total solids followed by clarification lowered the ash of the permeate. Constant agitation during crystallization with 80% ethanol (v/ v) at pH 2.5 yielded almost 88% lactose in 3 hr. Alcoholic acid addition (1%) at the end of crystallization time and agitation for 10 min was optimum to reduce entrapped impurities in the form of ash and protein. Lactose quality factors were comparable to commercial edible grade lactose. United States Pharmacopeia grade lactose was also produced using the ethanol-water mixtures.