The C-13 kinetic isotope effects in the catalytic oxidation of carbon monoxide over silver wool were found in the temperature range 343-453 K with the following temperature dependence : 100 ln(k(12)/k(13)) = (3.398-630/T) +/- 0.083. A reaction CO/O-2 gas mixture of 1:2 ratio was used in a static system with initial pressures ranging from 20 to 40 kPa. Under these conditions the reaction obeys the rate law dP(CO)/dt = -k(1)P(CO) and has an apparent activation energy of 59.3 +/- 1.7 kJ mol(-1). In our theoretical interpretation, based on Bigeleisen＇s formalism, various geometries of (CO2)double dagger were applied as transition states of the rate determining step, and only a (CO2)double dagger with an interbond angle of 110 degrees and stretching force constants of 1700 and 1000-1400 N m(-1) could explain the experimental results.