Using the Maedi-Visna virus strain WLC1 (Weybridge) and different cell lines of sheep plexus chorioideus we were able to establish and improve a production procedure of MV-antigen for use in immunodiffusion assay. Our attention was focused mainly on the efficient virus multiplication in cell cultures and on standardisation of the procedure to find a method keeping the antigen loss as low as possible. Investigations with our antigen in 39 farms of 5 of the former districts in East Germany revealed a seropositive reagent rate between 0 and more than 60%, underlining the need for a complex diagnostic and eradication programme.