Cell lines have been developed from 2-day-old embryos of the biting midge, Culicoides variipennis (Diptera: Ceratopogonidae). In North America C. variipennis is the primary insect vector of bluetongue virus (BTV), an orbivirus that causes disease of ruminants. The C. variipennis (CuVa) cells, grown in Schneider's Drosophila medium, consist primarily of a fibroblast-like cell type. CuVa cells are very hardy. They can grow over a wide range of temperature and pH and adapt to growth in minimal essential medium. BTV replicates to high titer (7.5-8.0 log10 50% tissue culture infectious doses/ml) in CuVa cells over a wide range of temperatures (19 degrees to 37 degrees C) without inducing any significant cytopathic effects. The highest BTV titers were obtained in CuVa cells grown at 25 degrees and 32 degrees C. Cells from C. variipennis can be useful for many diverse investigations.