Adsorption of proteins at all surfaces has a characteristic lagtime which can be monitored by surface tension at the air/water interface. The cause of the lagtime is not completely understood and there is little experimental evidence for what is happening on the molecular scale at the surface. Mixtures of proteins show surprising complexity in their lagtime behaviour.This both gives a means of experimental control and gives interesting information pertinent to the displacement behaviour. In comparison with an earlier experiment on INTER we have enhanced the sensitivity of the experiment with a better means of exchanging the surface and by the use of a perdeuterated protein. We propose to follow the behaviour of human serum albumin/maltose binding protein mixtures at the surface.