The aim of this study was to evaluate expression stability of four frequently used endogenous controls: β-actin, glyceraldehyde-3-phosphate dehydrogenase, β2-microglobulin and RNA polymerase II polypeptide A in peripheral blood mononuclear cells from war veterans with and without posttraumatic stress disorder (PTSD). The gene discussed is ACTB; the disease is post-traumatic stress disorder.