Sensory neurones from new-born rat nodose ganglia were grown in tissue culture, either with or without the ganglionic satellite cells, in order to investigate influences of satellite cells on sensory neurone development. To learn more about the post-natal development of nodose ganglia in rats neuronal counts of the ganglion were made at three different developmental stages. There were no significant differences of neuronal number in nodose ganglia in new-born rats, rats 3 weeks of age, and adult rats. Up to 60% of the neurones formed synapses with each other when they developed in culture without ganglion satellite cells. Pharmacological experiments indicated that the transmitter at these synapses was ACh and the post-synaptic receptors were nicotinic. Neurones co-cultured with satellite cells rarely formed functional synapses and most (85%) were not sensitive to ACh: 75% of neurones cultured without satellite cells were ACh sensitive. These results provide evidence that mammalian sensory neurones form synapses among each other in culture. The results also suggest that ganglionic satellite cells prevent functional synapses among these neurones from occurring, in part because the neurones do not express ACh sensitivity when co-cultured with satellite cells.