The genes encoding the inner core protein VP6 of African horsesickness virus (AHSV) serotypes 3 and 6 have been cloned and sequenced. The genes are 1169 nucleotides in length and both encode a largely hydrophilic protein of 369 amino acids. The VP6 amino acid sequence is highly conserved between the two serotypes with an overall similarity of 95 percent. Comparison of the AHSV VP6 amino acid sequences with those of bluetongue virus serotype 10 VP6 revealed that it is 41 amino acids longer with an overall amino acid identity of 29 percent. The similarity is mainly confined to a short but highly conserved 13 amino acid region at the N terminus, a short seven amino acid region at the C terminus and a 22 amino acid region close to the C terminus. Within this last region is a smaller 11 amino acid region from 318 to 328 with a 91 percent similarity to the Rep helicase of Escherichia coli.