Objective: The present study was designed to determine the effect of the freeze-thawing procedure, computer controlled rate freezing and duration for six months, on human sperm chromatin (assessed by acridine orange test), vitality, motility, and morphology.
Design: Experimental study
Material and Method: Twenty semen samples were obtained from patients attending the infertility unit. The semen analysis was measured according to WHO criteria. Sperm morphology was evaluated by strict Kruger criteria and sperm chromatin were detected by acridine orange test. After semen analysis, each sample was mixed with cryoprotectant and divided into straw. The straw was frozen with computer controlled rate freezing method. After 6 months of cryostorage, semen samples were thawed and then the semen was analyed, and sperm chromatin and morphology were determined.
Results: After six months of cryostorage, the mean percentage of normal sperm chromatin decreased significantly (87.3 + 9.0 vs. 51.9 + 27.4, p < 0.001). Vitality, motility, and normal morphology of sperm decreased significantly (78.7 + 1.9 vs. 32.8 + 10.8, 52.6 + 1.9 vs. 24.1 + 10.9 and 21.4 + 4.3 vs. 18.0 + 4.4 respectively, p < 0.001).
Conclusions: The computer controlled rate freezing of sperm for six months and thawing process significantly decreased normal sperm chromatin, vitality, motility, and normal morphology.

Keywords: Cryopreservation, Sperm chromatin integrity, Computer program freezer