We have determined the 1.5 A crystal structure of the Bacillus Anthracis str. Ames 12 kDa CsaA protein. Asymmetric unit structure revealed two molecules forming tight dimmer, highly likely the functional unit. The structure of the monomer closely resembles fold of oligonucleotide-binding proteins (PF01588). The two identical cavities on the protein surface are likely to constitute the substrate binding sites. The CsaA protein from B. subtilis, close homolog of B. Anthracis, is characterized as a chaperone with export-related activities.