Here we report the characterization of the human S100A13 cDNA coding for a novel calcium-binding protein belonging to the S100 protein family. The predicted S100A13 protein shows sequence homologies to other S100 proteins between 50.5% (to S100A5) and 59.3% (to S100A12). High mRNA amounts were found in skeletal muscle, heart, kidney, ovary, small intestine and pancreas. Since twelve S100 genes are clustered on human chromosome 1q21, we determined the chromosomal localization of the human S100A13. It co-localizes with S100A1 on the cluster. Furthermore, we characterized the cDNA sequence coding for the mouse homolog of S100A13. Similar to the putative human protein, mouse S100A13 is composed of 98 amino acids displaying a homology of 86.7% compared to human S100A13.