The discharge patterns of tonically-firing neurones are influenced by both the characteristics of their presynaptic input and their intrinsic properties. The regularity of the discharge of motoneurones is thought to reflect their prominent post-spike afterhyperpolarization (AHP). When a motoneurone fires at steady mean rate, the distribution of interspike intervals is determined by the amplitude and frequency content of the synaptic noise together with the decrease in excitability following a spike due to AHP. This paper considers how motoneurone discharge statistics can be used to estimate AHP trajectories as well as a motoneurone's sensitivity to excitatory input.