Recovery of ova was effected by slaughter of the donor and removal and flushing of the reproductive tract. A significantly greater percentage of ova were recovered from cows than from calves. Cow ova were fertilized at the rate of 61·49% while fertilization rate of calf ova was 23·6 %. A significantly greater percentage of cows, not possessing corpora lutea at breeding, produced more fertilized ova than did cows possessing a 'full-sized' corpus. The administration of stilboestrol to cows possessing 'full-sized' corpora lutea was observed to significantly increase the percentage of fertilized ova recovered from 14·29 to 66·6%. Also, the administration of stilboestrol increased the percentage of fertilized ova recovered from calves, and permitted the collection of fertilized ova from pregnant cows.