Ghrelin production was originally demonstrated in human endocrine cells of the gastric body and of the pituitary gland, but was rapidly shown to occur also in several other normal and neoplastic cells. Most endocrine tumors were found to contain ghrelin, as detected by both immunohistochemistry or mRNA analysis. Not only pituitary adenomas and gastro-entero-pancreatic carcinoids produce ghrelin, but also pulmonary carcinoids and thyroid tumors. In addition, we have shown here that nonendocrine lung, breast, colorectal, prostatic, and pancreatic carcinomas may produce ghrelin, as well. The significance of ghrelin expression in human tumors is poorly understood, but it is of interest that concurrent expression of ghrelin binding sites also occurs in many of the above listed neoplasms. Although only one ghrelin receptor has been cloned so far (the growth hormone secretagogue receptor), data from binding studies indicate that a family of ghrelin receptors probably exists in human tissues, including tumors. These receptors share the ability to bind acylated and nonacylated ghrelin, as well as synthetic analogs of the GH secretagogue family. In fact, in vitro experiments demonstrated the ability of these compounds to displace radiolabeled ghrelin from binding sites and also their antiproliferative effects on several human tumor cell lines. These findings open interesting perspectives in the control of tumor cell growth using synthetic ghrelin analogs. However, a complete mapping of the ghrelin receptor distribution in human tissues and, above all, tumors is necessary, together with the validation of in vitro data on in vivo models, to better define the effects of different ghrelin analogs on human tumor growth.