Reverse transcription-PCR (RT-PCR) was used to detect African horse sickness virus (AHSV). A single primer pair which amplified a 423-bp fragment of the S8 gene which encodes the NS2 protein of AHSV was identified. Amplification of this fragment from all nine serotypes of AHSV was achieved with these primers. Between 10(1) and 10(2) copies of AHSV genomic double-stranded RNA could be detected by RT-PCR followed by agarose gel electrophoresis and ethidium bromide staining. Application of RT-PCR to blood samples from AHSV-infected horses resulted in earlier detection of viremia than virus isolation did. Furthermore, viremia was detected by RT-PCR in blood samples from horses infected with an avirulent isolate of AHSV which were negative by virus isolation. AHSV was also detected by RT-PCR in spleen and lung samples from horses which died of AHSV infection. These results indicate that RT-PCR is a rapid and sensitive method for the identification of horses infected with AHSV.