We present theoretical and experimental data necessary for raising specific antibodies for thymosin beta 10, a 43-amino acid residues peptide occurring in human tissues. We postulate that thymosin beta 10 contains three major antigenic determinants (residues 2-8, 17-25, and 35-41). For antibody development, we synthesized the N-terminal fragment thymosin beta 10(1-16) as well as the C-terminal fragments thymosin beta 10(31-43) and thymosin beta 10(38-43), due to their putative antigenic properties and minimal structural similarity with the homologous peptide thymosin beta 4, which also occurs in humans. The putative antigenic determinant 17-25 is present in all beta-thymosins and was therefore not synthesized. All antisera raised against the above peptide fragments or the intact molecule of thymosin beta 10 were found capable of recognizing and binding synthetic or natural thymosin beta 10 with high specificity, showing minimal cross-reactivity with thymosin beta 4 isolated from bovine tissues or synthetic thymosin alpha 1. Due to its easy preparation and the highly specific affinity of the antibody raised against it for the intact peptide, the fragment thymosin beta 10(38-43) may be considered the antigen of choice for developing anti-thymosin beta 10 antibodies, which can eventually be applied to immunochemical studies.