The human thymus is under the control of the autonomic nervous system (sympathetic and para-sympathetic nerve fibres). Moreover, somatic fibres reach the thymus through the phrenic nerve.  To study the role of some peptidergic nerve fibres in the human thymus, in order to add new data on thymus neuroimmunomodulation.  Morphological observations were carried out on samples of human thymus harvested during biopsies. Immune-histochemical staining for some neuropeptides was performed. All our data underwent morphometrical analysis (quantitative analysis of images and statistical analysis of data). Our results provide direct evidence of the presence in the human thymus of the following neuropeptides: neurotensin, neuropeptide Y, vasoactive intestinal polipeptide, protein gene product 9.5 and substance P. The presence of specific neuropeptides in the human thymus suggests that a special neurotransmission is required for the induction of its immune role; furthermore, also the development and maturation of thymus cells is under the control of the autonomic nervous system. Studies on neuropeptides in the human thymus are the first step for the confirmation of neuroimmunomodulation in this lymphoid organ.