•  In the rat, unlike in other species, motoneurones of both the internal intercostal nerve and the external intercostal nerve show a phase of excitation in expiration. •  This study investigated the pathways transmitting this excitation from the medulla. •  Direct (monosynaptic) excitation was found from individual expiratory neurones in the medulla to internal intercostal nerve motoneurones, but only indirect (disynaptic) excitation was found from the same neurones to the motoneurones of the external intercostal nerve. •  This is the first demonstration of two separate pathways from individual long descending fibres specific to two different sets of motoneurones. •  This specificity could be useful in studying plasticity or regeneration in thoracic segments in investigations of mechanisms involved in spinal cord injury and repair. Abstract  The respiratory activity in the intercostal nerves of the rat is unusual, in that motoneurones of both branches of the intercostal nerves, internal and external, are activated during expiration. Here, the pathways involved in that activation were investigated in anaesthetised and in decerebrate rats by cross‐correlation and by intracellular spike‐triggered averaging from expiratory bulbospinal neurones (EBSNs), with a view to revealing specific connections that could be used in studies of experimental spinal cord injury. Decerebrate preparations, which showed the strongest expiratory activity, were found to be the most suitable for these measurements. Cross‐correlations in these preparations showed monosynaptic connections from 16/19 (84%) of EBSNs, but only to internal intercostal nerve motoneurones (24/37, 65% of EBSN/nerve pairs), whereas disynaptic connections were seen for external intercostal nerve motoneurones (4/19, 21% of EBSNs or 7/25, 28% of EBSN/nerve pairs). There was evidence for additional disynaptic connections to internal intercostal nerve motoneurones. Intracellular spike‐triggered averaging revealed excitatory postsynaptic potentials, which confirmed these connections. This is believed to be the first report of single descending fibres that participate in two different pathways to two different groups of motoneurones. It is of interest compared with the cat, where only one group of motoneurones is activated during expiration and only one of the pathways has been detected. The specificity of the connections could be valuable in studies of plasticity in pathological situations, but care will be needed in studying connections in such situations, because their strength was found here to be relatively weak.