By ultrafiltration of skim milk a new low-lactose milk powder was developed whose lactose content was reduced by 86%. The lactose was replaced by malto-dextrin. In contrast to lactose-hydrolyzed milk powder, no protein-destroying processes (Maillard reactions) could be demonstrated during production or after storage at standard conditions. Tolerance of the new low-lactose milk versus regular skim milk was tested in 35 well-nourished, adult Latin Americans with lactose malabsorption. The ingestion of 500 ml of the low-lactose milk gave rise to significantly (p less than 0.05) fewer symptoms than regular skim milk. After the intake of 250 ml there a tendency to fewer symptoms after the low-lactose milk, although the difference was not significant (0.05 less than p less than 0.1). The new milk may be of potential usefulness in the treatment of protein calorie malnutrition in the developing countries, where lactose malabsorption is highly prevalent.