In this study, goats were experimentally infected with caprine arthritis-encephalitis virus (CAEV). Anti-CAEV antibodies were detected in vivo using indirect enzyme-linked immunosorbent assay (ELISA) and Western blot assays. The results showed that the sensitivity of detection of anti-CAEV antibodies using indirect ELISA was relatively high, whereas Western blotting was very sensitive for detection of P28 anti-CAEV antibody as 4 days postinfection. Apparently, because of high immunogenicity of P28 antigen, the detection of antibodies specific for this viral protein may represent a valuable assay to detect early infection. CAEV related to other lentiviruses may be useful in studies of human immunodeficiency virus (HIV) and related viruses in animal models.