Peripheral nerve 'pseudoganglia' are described in the literature with little focus on histology. The phrenic ganglia, which are located on the inferior surface of the diaphragm and are associated with the phrenic nerves, have been described by some authors as potentially sympathetic ganglia although this, to the authors'knowledge, has not been proven. The purpose of the present study was to elucidate further the true autonomic nature of this collection of nerve cell bodies. In eight fresh adult cadavers <6 h after death, the left and right phrenic ganglia were harvested and subjected to immunochemistry. All phrenic ganglia were vasoactive intestinal polypeptide negative but tyrosine hydroxylase positive. These findings indicate that the phrenic ganglia are sympathetic ganglia with most likely a vasomotor function. © 2008 The Authors Journal compilation © 2008 Japanese Association of Anatomists.