54 white rats were studied physically, histochemically and morphometrically for the effect of EHF electromagnetic field on repair of the lung surfactant system. The damage was inflicted by acute hypoxia existing at the altitude of 9000 m above the sea level simulated in the chamber. For the period studied natural repair was unable to secure the return to normal structure and function of the surfactant system, whereas daily 20-minute exposures to millimetric waves on the chest stimulated repair on after-exposure day 1-5 and provided normalization of all the physical and morphometric parameters.