The effect of various diluents, dilution rates, freezing and thawing methods, glycerol concentrations, glycerol equilibration temperatures, holding temperatures after thawing, equilibration times and freezing preservation periods on the viability of chicken spermatozoa were examined and the fertility test was carried out successively. The results were summarized as follows.
1. Diluent A was the most effective in maintaining motility and percentage of motile sperm and Diluent B was the most effective after Diluent A. The effect of Diluent C, D, Locke-Ringer solution and Yamane's solution were clearly inferior to that of Diluent A and B.
2. As for the dilution rates on deep freezing of the chicken semen the buffer diluted for four times was superior to the buffer diluted for eight times and it seems to be necessary for freezing preservation of chicken spermatozoa not to rise the dilution rate.
3. In the case of freezing the chicken spermatozoa, Method 4 was the most effective in maintaining the motility and percentage of motile sperm of the three and Method d) was the most effective of the four in the case of thawing the chicken spermatozoa after freezing.
4. The glycerol concentration of 7 percent was the most effective to protect the survival of chicken spermatozoa thawed out after freezing in the present experiment.
5. The semen samples equilibrated at 5°C was the most superior in maintaining the motility and percentage of motile sperm as compared with that of 10°C and 20°C.
6. The holding temperature of 20°C after thawing was the most effective in maintaining the viability of chicken spermatozoa and 30°C and 37°C ranked to it in order.
7. The semen samples equilibrated at 5°C for 60 minutes gave higher motility and percentage of motile sperm than those of 30, 90 and 180 minutes.
8. There were no remarkable differences between the resumptions of motility of chicken spermatozoa and storage periods when the semen samples stored for 1, 7, 14, 30 and 90 days.
9. The striking differences among fertility when the semen samples stord for 30, 90 and 100 days respectively at -79°C were not observed.