A technique is described by which the vaccine strain of bluetongue virus (BTVV) may be isolated from infected fetal, neonatal, and adult sheep tissues utilizing tissue culture. The data from these studies provides evidence that 1) BTVV can be readily isolated from infected fetal and newborn tissues by tissue culture, 2) mild treatment of tissues and utilization of lysed cells as inoculum an effective means of recovering vaccine virus, 3) BTVV can be isolated with equal efficacy from mononuclear fractions and from erythrocyte granulocyte fractions of viremic blood, and 5) the brain of fetal lambs and the spleen and liver of neonatal lambs appear to be the tissues from which vaccine can be consistently isolated.