Received December 14, 1999
Accepted January 15, 2000

The objective of this descriptive clinical study was to evaluate whether some spermatic parameters and number of mature oocytes, have influence with regards of fertilization "in vitro" of human gametes. Ninety eight samples of semen and 678 oocytes of couples, attended at the Infertility Clinic of Unicamp, were analyzed. For the data analysis, the dependent variable were the occurrence or not of fertilization of the oocyte "in vitro" and the rate of fertilization "in vitro". The variables with greater influence in the fertilization of the oocyte "in vitro" were: grade A motility and the amount of mature oocytes. Data obtained from the ROC curve showed that the cut point for the percentage of spermatozoa with grade A motility was >30/<30, with sensitivity and specificity values at 65.2% and 65.5% respectively. Based on these values, the odds for fertilization, when the percentage of motile grade A spermatozoa is greater than 30%, was 1.89.