Semen from each of six bulls was used to study the effects of percent glycerol and rate of freezing on spermatozoa extended in egg yolk-sodium citrate extender and packaged in .25-ml Continental straws. Treatments were arranged factorially and included 5, 6, 7, 8, 9, 10, or 11% (volume/volume) glycerol; freezing rates (time from 5 to -130 C) of 1, 2, 3.5, 7, 12, or 20 min; and post-thaw incubation times of 0 and 2 h at 38 C. Post-thaw motility was similar for spermatozoa frozen in 2 to 20 min, and all means were greater than for spermatozoa frozen in 1 min. Post-thaw motility of spermatozoa frozen in 7% glycerol did not differ from that with 5 to 9% but was superior to that with 10 or 11% glycerol. Although glycerol and freezing rate interacted, 7% glycerol provided survival equal to or greater than that with the other percents of glycerol, regardless of freezing rate.