Five new candidate genes for fatness, growth, and feed intake traits were studied. The genes were chosen based on their presumed biological action for a given trait of interest. A molecular genetics polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) approach was used to identify genetic differences (polymorphisms) in the porcine melanocortin-4 receptor (MC4R), melanocortin-5 receptor (MC5R), cocaine and amphetamine-regulated transcript (CART), peroxisome proliferator activated receptor _ (PPAR_), and prepro-orexin genes. These genes were genetically mapped using several markers on porcine chromosomes (SSC) 1, 6, 12, 13, and 16, respectively. All five genes also were physically mapped with a pig/rodent somatic cell hybrid panel. The physical locations of all five genes are as follows: MC4R (SSC1q22-27), MC5R (SSC6q24-(1/2)q31), prepro-orexin (SSC12p13- p11), PPAR_ (SSC13q23-q41), and CART (SSC16q21). The localization of these genes is reasonably consistent with previous chromosome painting results, indicating conserved (similar) regions between human and pig chromosomes. We also looked at the effect of these genes on traits of interest. The effect of a MC4R polymorphism was investigated in a large population of pigs from several commercial lines. MC4R genotypes were significantly associated with fatness, growth rate, and feed intake traits. Further studies on the effect of these candidate genes are underway.