Human semen samples may show sample to sample (inter-sample) vari­ability of sperm parameters due to multi-factorial nature of sperm pro­ duction and transport through male reproductive tract. We reviewed charts of I 09 men referred to the Sperm Bank at Cleveland Clinic Foundation.

We compared inter-sample variability of pre-freeze and post-thaw (24hours after freezing) sperm motility and motion kinetics [average path velocity (YAP), straight-line velocity (VSL), curvilinear velocity (VCL),

linearity (LIN) & amplitude of lateral head displacement (ALH)] of cry­opreserved semen collected at 2-3 days intervals. Patients were classified into S groups: infertile men (n = 19), testicular cancer (n =22), Hodgkin's disease (n =15), lymphoma (n =18), and other cancers (n =19). Semen

samples collected from 16 fertile men, prior to vasectomy, served as con­trols. Two to 4 samples were collected from each individual. The post­ thaw variability of sperm motility, VSL, YAP, LIN & ALH were signifi­cantly higher than pre-freeze variability (P<0.000 1, 0.02, 0.006, 0.009 &

0.0001; respectively). The increase in post-thaw variability was equally

observed in fertile and infertile men, and in men with different testicular pathologies. Post-thaw variability was not correlated with individual's age, length of disease, history of smoking, or alcohol intake.

In conclu­sion, semen samples collected for cryopreservation may show a high degree of post-thaw variability of sperm motility & motion kinetics despite low degree of pre-freeze variability. Further research is required to explain the exact mechanism(s) of such phenomenon, which may help select ideal samples for cryopreservation.