Analyses of the heat flow for all 7 NAGRA deep drill holes were carried out using the Bullard Plot and the interval method. The dependence on temperature of the heat conductive properties were taken into account and corrected. There is a linear relationship between the heat productivity of the Herzynian primary rocks and the heat flow, which is valid for steady temperature ratios. Deviations from this relationship point to increased or reduced heat flow. figs., tabs., 33 refs.