We report the technique for determining the orientation of the Ige molecules in Langmuir films immobilized on a solid substrate. This technique is based on measuring the binding of the secondary antibodies specifically recognising Fab and Fc fragments of immobilized IgG molecules. Specific binding of anti-Fab and anti-Fc rabbit anti-mouse (RAM) polyclonal antibodies to the film of mouse IgG shows strong dependence on surface deposition pressure of the film indicating changes of molecular orientation occurring in the film. At high deposition pressures the amount of anti-Fab specific RAM antibodies bound with the mouse IgG film is much greater than the anti-Fc specific RAM antibodies. This means that IgG molecules of the film are preferentially oriented with their Fab fragments outside. The ratio of molecules oriented in this way to the opposing molecules is estimated to be 3.125. The technique can be considered rather general and suitable for similar studies of any protein 2-dimensional arrays since the antibodies to different parts or fragments of any protein can be obtained.