The melanocortin-4-receptor gene (MC4R) is a key regulator of energy homeostasis, food intake and body weight. MC4R gene mutations are associated with early-onset severe obesity. Most patients are heterozygotes, with some reports of homozygotes and compound het-erozygotes. The authors report a case involving an eight-year-old girl with progressive weight gain from infancy, body mass index 44 kg/m: (>97th percentile), hyperphagia, hvperinsulinemia and increased linear growth. There was no phenotvpe of morbid obesity in the parents or sibling. Coding regions and intron-exon boundaries of the genes encoding leptin, Ieptin receptor, pro-opiomelanocortin and MC4R were analyzed. Two heterozygous coding mutations in the MCR4 gene (S94N and C293R) were detected, of which the second has not been previously reported. The mutations were on opposite chromosomes, confirming compound heterozygosity. The molecular findings and clinical features associated with this novel MC4R mutation are described. The authors emphasize that rare mutations can be found in some patients with severe childhood-onset obesity.