Because relatively few caprine arthritis-encephalitis virus (CAEV)-infected animals exhibit clinical signs of illness, efforts to control and eradicate this virus will depend heavily on a sensitive diagnostic test that can be easily carried out. The currently utilized tests are of limited usefulness because of relatively low sensitivity or because of incomplete cross-reactivity of goat sera with heterologous test antigens. An enzyme-linked immunosorbent assay (ELISA) with purified CAEV antigen and biotin-avidin amplification steps was therefore developed and compared with a radioimmunoassay (RIA) against CAEV p28. Of over 500 sera tested, there was 99% concordance between the two tests. On the other hand, 23 of 24 sera obtained from animals with clinical signs of disease that were negative by agar gel immunodiffusion test (with ovine progressive pneumonia virus antigen) were positive by ELISA and RIA. These results suggest that an ELISA with CAEV antigen is superior to the agar gel immunodiffusion test and is easier and faster than an RIA, and therefore may be the method of choice for diagnosing CAEV infection.