<p>In a process for preparing an indole by reacting an aniline with a diol, a catalyst the activity of which has been reduced through its use in the reaction is brought into contact with an inert gas containing 5 vol.% or less of oxygen so that the catalyst is regenerated for its repeated utilization. The activity of the regenerated catalyst is enhanced further when it is subjected to a reducing treatment for actuation upon its reutilization.</p>
