A study was performed to examine microclimate in 14 stables belonging to 10 horsemen's teams and clubs; five of these houses were new-built. In five race-horse stables housing 16 horses each, on an average, where the optimum air temperature ranged from 10 degrees C to 12 degrees C, measurements and examinations were performed in the winter period and the following results were obtained: space per 1 horse housed 42.9 plus or minus 8.7 m-3, relative air humidity 74.3 plus or minus 3.8%, CO2 concentration 0.175 plus or minus 0.027%, NH3 concentration 0.00135 plus or minus 0.00044%. A large majority of horse stables under our conditions lack suitable ventilating equipment for winter and for cold periods. Together with the present-day building technology and with excessive space of box-type houses, this implies that microclimate conditions are unsuitable and harmful to health; in particular, this is true of cold and wet conditions. In the existing stables this problem can be solved by additional heating, preferably with the hot-air system. It is necessary that horse stables should have good thermal-insulation characteristics, with plastered brick walls 45 cm in thickness and with thermally insulated loft. Floors must be solid, hard, and plane. Modern building technology and new materials must secure all the required parameters, with due respect to all factors constituting microclimate and to purposeful layout of race horse stables. It appears desirable to issue a state standard for the construction of horse stables.