A lyophilization method for long-term preservation of the initial bioluminescence of Photobacterium phosphoreum was investigated. The initial bioluminescence of lyophilized P. phosphoreum at different temperatures, .20 ℃, 4 ℃, room temperature (16-25 ℃) and 45 ℃, was monitored for 6 months with different additives. Saccharose, skim milk, and a mixture of saccharose and skim milk were tested. Skim milk showed the best protection for bioluminescence among the additives used. The initial bioluminescence remained high during 6 months at a wide range of storage temperatures, i.e., .20 ℃, 4 ℃, and room temperature, with skim milk as an additive. The average bioluminescence of lyophilized P. phosphoreum using skim milk as additive reached 33392 RLU within 30 min of regeneration. Bioluminescence increased slightly after 10 h of incubation.