The mechanism of incorporation of copper in amorphous films of Ge15Te85-x Cu-x (0 less than or equal to x less than or equal to 7 at.%) system and the effect of heat treatment are studied by measuring the de conductivity in the temperature range (150-423 K). The results indicates that there are two conduction mechanisms. For temperature above 330 K, conductivity exhibits activated behaviour, while in low temperature range (T = 150-300 K) conductivity exhibits non-activated behaviour. In the high temperature region, resistance and the activation energy have been calculated. The decrease in the activation energy on addition of Cu has been interpreted according to the Kastner model. In the low temperature region Mott's parameters have been evaluated and they are decreased with Cu content; the results in this region are interpreted following Mott's model.