Received October 21, 1998
Accepted February 16, 1999

Introduction:Techniques of assisted fertilization are giving new hope for couples who search for clinics specialized in artificial fertilization. Semen samples must be cryopreserved and most of the time, after unfreezing, there is a significant loss in motility associated to functional and structural defects who lead to bad semen quality and lessened fertilization rates. Our aim is to evaluate the best cryopreservation media for human spermatozoa based in a temporal analysis of semen quality comparing glycerol to Test-yolk Buffer(TYB). Material and Methods: Semen samples were obtained from 10 healthy volunteer individuais. The ejaculates were collected after two days of sexual abstinence. Samples were divided in two equal aliquotes which were cryopreserved with glycerol or with Test-yolk Buffer. Sperm samples were analised at O, 60, 120, 180 minutes after unfreezing and data was collected for morphology, motility, cellular swelling and cervical mucus penetration. Sperm viability was assessed by eosin-nigrosin staining and the results were statistically analised. Results:Both media used for cryopreservation led to significant loss in semen motility and viability. TYB was superior to glycerol as a criopreserving media due to better results regarding sperm motility and viability. All samples showed abnormal sperm morphology, independently of the used media. Conclusions:Samples cryopreserved with TYB had sperm motility less diminished when compared to samples where glycerol was the used media. The results were the same when regarded sperm viability and morphological and functional characteristics. We verified that TYB w as better than glycerol for cryopreservation and we recomend its use for human semen storage.