The t(time)- and T(temperature)-dependence of the conductivity of polyaniline and polyindoline has been measured in situ. Both polymers were synthesized electrochemically on gold electrodes by three different methods : by potentio-dynamic cycling, by a potential jump method and at a constant electrode potential. Measurements of the t-dependence showed a decreasing conductivity during the first 1000min down to between 55% and 95% of the initial value, depending upon the polymerization method. T-dependence measurements showed an increase of conductivity in the temperature range from 5 to 65 degrees C, beyond 75 degrees C (at polyindoline 65 degrees C) the conductivity decreased rapidly. The interpretation of the T-dependencies below 65 degrees C using the Arrhenius equation gave activation energies of the conductivity between 0.14 and 0.27 eV for both polymers, depending upon the mode of preparation. This is in close agreement with spectroscopic data. The irreversible decrease of conductivity beyond 65 (75)degrees C is accompanied by a modification of the cyclic voltammogram of the investigated polymer.