Deactivation of Raney nickel is studied using the methanation rate data in a plug-flow reactor. It is shown that a model consisting of a constant and a monoexponential term describes the deactivation rate data very well suggesting that the catalytic activity of nickel is controlled by two components. One component seems to show a steady catalytic activity where the activity of the other component appears to decline exponentially. Transient tracing of the methanation on Raney nickel using (CO)-C-13 indicates that these correspond to two forms of intermediates adsorbed on two distinct catalyst sites. These findings are supported by rigorous statistical analyses of the correlation between model parameters and the goodness of the fit of data to the model.