Freezing for a duration of one hour followed by thawing did not cause any detectable change in infectivity and sucrose density gradient centrifugation profiles of a purified preparation of carnation mottle virus (CaMV) suspended in 10mM potassium phosphate buffer (P. B.), pH 7.0. Infectivity of purified CaMV decreased considerably after 38-51 months of storage under frozen conditions at-20 C. However, the infectivity was maintained at a high level for 38-51 months by the addition of peptone or glycerol, etc. At-70 C, the virus remained highly infective for a long period without any additives. The infectivity of the purified CaMV decreased markedly when freeze-dried at pH 5.5-8.5 and subsequently suspended in P. B. The virions of these preparations became swollen at pH higher than 7.5 and aggregated at pH 5.5-6.0. But, the changes in the conformation of CaMV virions due to freeze-drying were prevented by the addition of lysine. The protective effect of additives during preservation of freeze-dried preparations was assessed at 65 C. The viral preparation freeze-dried in P. B. lost its infectivity within one day, but the preparation supplemented with lysine remained highly infective even after 7 days. The preservation conditions for CaMV were similar to those for southern bean mosaic virus which is physicochemically similar to CaMV.