Histological and immunohistochemical methods were used to study pelvic paraganglia in a series of human postnatal specimens ranging in age from 1 month to 6 y. Up to 5 months of age, many of the encapsulated paraganglia contained small pacinian-like sensory corpuscles which occurred either singly or in small clusters, implying an unknown functional interrelationship during this period. In older specimens, this intimate association was not observed since pacinian corpuscles and small nonencapsulated clusters of paraganglion cells were observed only as separate structures. It is suggested that the paraganglion cells may induce the formation of the pacinian corpuscles during fetal development. Immunohistochemistry using the nerve marker protein gene product (PGP 9.5) demonstrated a rich plexus of varicose nerve fibres within the paraganglia which may directly innervate the paraganglion cells and/or be associated with the profuse vascular supply. A similar density of vasoactive intestinal polypeptide-containing nerves was also demonstrated while some of the nerves contained calcitonin gene related peptide or substance P. The paraganglion cells stained positively for tyrosine hydroxylase, dopamine-beta-hydroxylase and neuropeptide Y, but not for phenylethanolamine N-methyltransferase. This combination of immunostaining confirms them as a rich source of noradrenaline.