Viability of bifidobacteria in freeze-dried probiotic products at various temperatures during prolonged storage was assessed. Bifidobacterium longum and Bifidobacterium infantis were freeze-dried. The freeze-dried preparations were stored at -18,4, and 20℃. Cell counts were enumerated using BS agar at 37℃ for 48 h under anaerobic conditions at 0, 45 and 120 days. Storage at 20℃ showed the greatest decline in the viability of bifidobacteria, whereas that at -18℃ showed the least decrease.