The sequence of the starch-binding domain present in 10% of amylolytic enzymes of microbial origin and classified as the carbohydrate-binding module family 20, was identified in the equivalent part of sequence of human genethonin, a skeletal muscle protein of unknown function. The sequence identity between the starch-binding domain from Bacillus sp. strain 1011 cyclodextrin glucanotransferase and the corresponding segment of human genethonin was higher than 28%. The amino acid residues known to be involved in the raw starch binding were found to be conserved in the genethonin sequence. The three-dimensional structure of the genethonin starch-binding domain was modelled and its eventual function briefly discussed.