Sentinel herds at 34 farms were used to study the epidemiology of bluetongue and related orbiviruses in Oman. The results indicate that bluetongue virus (BTV) is widespread and is enzootic in Northern Oman. At least three BTV serotypes (3, 4 and 22) were present at the time of the study. Antibodies to epizootic haemorrhagic disease of deer virus (EHDV) type 2 and EHDV-318 were also detected but were less prevalent. Entomological investigations identified the presence of 16 species of Culicoides. The peak seasonal incidence of the BTV vector C. imicola and the EHDV vectors C. schultzei (group) midges at Rumais in Northern Oman correlated closely with the spring rains in that area. However, both species of midge were also present in lower numbers throughout the year. Four species of Omani midge, C. arabiensis, C. ibriensis, C. neoschultzei and C. buettikeri are new to science.