Highly purified preparations of Chikungunya virus (CHV) were obtained from culture fluid of infected VERO cells (Green monkey kidney stable cells) by differential centrifugation involving sedimentation through 25% sucrose solution and density gradient centrifugation by the use of potassium tartrate (17 to 27 %). When the suspension of32P labeled purified CHV was fractionated with acid,32P was recovered mostly from the ribonucleic acid (RNA) and the lipid fraction. The base composition (per 100 nucleotides) of CHV-RNA was U=23.5, G=21.0, C=22.5, and A=33.0.