SummaryA sensitive protein immunoblotting (Western blot) procedure has been developed for detecting anti‐BLV antibodies in cattle sera. The antibodies against most of the major viral proteins could be detected. This procedure does not give any non‐specific background staining and there is absence of any erroneous results due to utilisation of purified viral preparations. The procedure has been applied for detection of antibodies to BLV in a set of 74 sera samples and it has been compared with other commonly used serological tests like ELISA and agar gel immunodiffusion t