[en] An analytical model for pulsed-neutron borehole gauges is developed. It takes into account the decrease of the γ-flux due both to thermal neutron absorption and to the movement of the neutrons away from the source. The model is one-dimensional, i.e. the effect of the borehole is not included. The fast neutrons are treated by use of Fermi-age theory, the thermal neutrons by use of diffusion theory. In the present version of the model the γ-detector is assumed to be very close to the pulsed source. The contribution of the scattered capture-γ-quanta to the γ-flux at the γ-detector is calculated by use of build-up factors. Numerical examples of the use of the model are presented. The model is compared with the usual, simplified model which assumes an exponential decay of the γ-detector count-rate. Formulas for the neutron slowing-down time and the thermal neutron lifetime are also presented together with numerical values of these lifetimes for various media of geological relevance. (author)