Simian Acquired Immunodeficiency Syndrome (SAIDS) is an important disease in captive primates in the United States associated with an unusually high mortality rate. Isolation of a type D retrovirus as the cause of SAIDS was rapidly followed by the development of an enzyme linked immunosorbent assay (ELISA) to determine the exposure of rhesus macaques (Macaca mulatta) to this virus. With increased use of the ELISA, a better understanding for interpretation of results was needed. One hundred thirty-one rhesus macaques were tested for the presence of antibody against SAIDS type D retrovirus (SRV) by both ELISA and Western blot techniques. Sensitivity, specificity and predictive values for the SAIDS ELISA were calculated for two populations based on a comparison with Western blot results. Sera was tested from two distinct populations, an endemic and a control population. Seventy-one macaques from a half-acre outdoor corral where SAIDS was first recognized made up the endemic population. Sixty rhesus macaques from both indoor and outdoor areas where the disease was not recognized made up the control population. This study has shown the ELISA to be a useful screening tool based on its high sensitivity for both endemic and control populations. This screening method provides a rapid and economical way to diagnose and manage SAIDS in captive non-human primate colonies.