The study concerns the problems and prediction of room flow in air-conditioning. It is shown how difficult it is to form mathematical models, especially of the three-dimensional flow field occurring in practice. After basic definitions, an explanation of the influence of different air flow systems on the structure of room flow is given. The microstructure of the flowis so complex that a precise mathematical model formation seems to be impossible. Measurements on isothermal and models(reduced from the original)supply reliable three-dimensional results. Similarity-theoretical studies indicate that model tests are principally a useful means of increasing the dimensional certainty, but in order to exactly reproduce the three-dimensional room flow, the test in the scale 1:1 remains essential.