Ruthenium catalysts deposited on active carbon and pre-calcined at 1900 degrees C in He atmosphere were studied. The precursors of the active phase were RuCl3 . 0.5H(2)O and Ru-3(CO)(12). Potassium and cesium (hydroxides or nitrates) were used as promoters. The catalysts were characterized by TEM, WAXS and H-2 chemisorption. Activity measurements in NH3 synthesis were performed in a flow integral reactor under a pressure of 10 MPa at 470, 430, and 400 degrees C (H-2 : N-2 = 3 : 1). It has been found that the alkali-promoted catalyst deposited on the thermally modified carbon is much more active than that based on untreated carbon. The form of the Ru precursor used in the manufacture of the K-promoted catalyst had no effect on its dispersion or activity. The promoting effect of potassium was comparable to that of cesium. A monotonous increase in the activity of alkali-promoted catalyst vs. Ru content (5-15%) was observed, accompanied by a decrease in dispersion.