Synaptic like microvesicles (SLMV) form a pleiomorphic population of vesicles present in neuroendocrine cells of the pituitary and the adrenal medulla. Their composition and biogenesis is very similar to small synaptic vesicles (SSV) present in nerve terminals. Membrane proteins of SSV involved in fusion (synaptotagmin) and trafficking (Rab 3) together with synaptophysin have been identified on SLMV. The SLMV from pancreatic beta cells store GABA, those present in chromaffin cells catecholamines and/or acetylcholine. We conclude that SLMV may participate in regulated exocytosis based on (a) their localization near release sites, (b) their content and (c) their membrane composition. The functional meaning and the way this process is regulated remain to be elucidated.