Melanin-concentrating hormone (MCH) is a cyclic, 19 amino acid peptide produced in the lateral hypothalamus and other regions of the mammalian brain (Bittencourt et al., 1992). When administered intracerebrally or overexpressed transgenically in rodents, MCH stimulates food intake and weight gain (Ludwig et al., 2001). A receptor for MCH, previously identified as an orphan receptor SLC-1 and renamed MCH1, has been identified in humans and rodents. Consistent with a role in hypothalamic control of feeding behavior, MCH1 is expressed in in the ventromedial and dorsomedial nuclei of the hypothalamus (Chambers et al., 1999). Genetic ablation and pharmacological antagonism of MCH1 in rodents results in resistance to obesity caused by a high fat diet or leptin deficiency (Borowsky et al., 2002; Segal-Lieberman, et al., 2003; Shearman et al., 2003; Marsh et al., 2002; Chen et al., 2002). Thus, MCH1 is an attractive target for obesity. Cloned human MCH1-expressing cell line is made in the Chem-1 host, which supports high levels of recombinant MCH1 expression on the cell surface for functional detection via the calcium signaling pathway. Thus, the cell line is an ideal tool for screening for agonists, antagonists, and modulators at MCH1.