The effect of the resistance to interface mass transfer on the overall rate of the hydrodechlorination of carbon tetrachloride has been analyzed with a 1% Pd/carbon catalyst, in a bubble column slurry reactor. The reaction was carried out at 393 K and 3 MPa. The effect of catalyst concentration on the external diffusion was analyzed for 7.96,19.09, 39.77 and 63.64 g I-TTCM(-1) (0.5,1.2, 2.5 and 4 wt%, respectively) with an H-2 flow F(H-2) = 24 x 10(3) N cm(3) h(-1) and an average particle size of the catalyst, d (p) = 75 mum. The importance of the gas-liquid resistance for F(H-2) = 3 x 10(3), 12 x 10(3), 18 x 10(3), 24 x 10(3) and 30 x 10(3) N cm(3) h(-1) was investigated with a catalyst concentration of 1.2 wt%. The effect of d (p) for 25, 75 and 130 mum was similarly studied for F(H-2) = 24 x 10(3) N cm(3) h(-1) and 1.2 wt% of catalyst. The analysis was performed using the equation C-i/(-R-H) = (d(b)/6epsilonk(g,1)) + 1/m[d (p)rho(p)/6 k(l,c) + 1/k(s)eta], which correlates the overall reaction rate (-R-H) with the mass-transfer rates at the interfaces gas-liquid and liquid-solid, the diffusion inside the pores and the surface reaction rate. The results indicate that the resistance to hydrogen transfer from liquid to the external surface of the catalyst does not affect the overall reaction rate, at least up to a catalyst concentration of 2.5 wt%. For F(H-2) greater than or equal to 24 x 10(3) N cm(3) h(-1) the gas-liquid resistance is lower than 5% of the total resistance and, therefore, does not control the overall rate of the process. Using theoretical equations, the mass-transfer parameters required for a scale-up of the process have been calculated. For d (p) less than or equal to 75 mum, the process is essentially controlled by the surface chemical reaction. Additionally, it was verified that the gas-induced agitation produced by a flow of 24 x 10(3) N cm(3) h(-1) is equivalent to that produced by a mechanical agitator working at 1500 rpm in a stirred-tank slurry reactor, under the same experimental conditions.