The surface composition of spray-dried mixtures of lactose/protein and lactose/glycine were estimated by means of ESCA. The results show that even with a low concentration of protein (0.01% wt) in the solution to be dried, protein starts to appear on the surface of the powder. At a protein/lactose ratio of 1/99 the protein starts to dominate the powder surface. At a protein/lactose ratio of 20/80, ~70 % of the surface is covered by protein. The results are similar for the proteins sodium caseinate and bovine albumin. The spray-drying of mixtures of lactose/glycine gives a different result. In this case, the surface composition of the powder reflects the composition of the mixture to be dried The surface tensions of the solutions show that the proteins have a higher surface activity than lactose, since even a small amount of protein added to a lactose solution lowers the surface tension considerably. Glycine affects the surface tension to only a minor extent. These results show that the composition of the air-water interface of the drying droplets is reflected in the surface composition of the dried powder. In addition, scanning electron microscopic pictures show that the changes in the powder structure when protein is added to the solution are associated with the presence of protein on the surface. When the surface coverage of protein increases, dents start to appear on the particles. The powders made from lactose/glycine solutions are highly agglomerated regardless of the glycine concentration.