Synchronization of ovulation is a common reproductive management practice in the US dairy cattle industry. The objective of this study was to compare two different sites of hormone administration (intralabial versus intramuscular) and two different manufacturers (Parnell versus Zoetis) of the reproductive hormones gonadotropin releasing hormone (GnRH) and prostaglandin F2α (PGF) on the efficacy of ovulation induction. Holstein cows (n=388) were enrolled in a pre-synch/ovsynch protocol during this 14-month study. Ultrasonographic observation of ovaries was made eight days after timed artificial insemination (TAI). Overall, treatment had no effect on the proportion of cows (90.0%) that ovulated in response to treatment. The incidence of double ovulations was 20.6% but was not affected by treatment. Similarly, treatment had no effect on the incidence of ovarian cysts (8.8%). Results revealed that failure to ovulate in response to exogenous hormone treatment caused a 10% reduction in potential pregnancy rate. There was no difference in efficacy of ovulation induction due to manufacturer of products, indicating that producers have a choice of products they can use. Intralabial administration of reproductive hormones was equally effective as intramuscular injection for the induction of ovulation, and intralabial injection should be considered a viable administration site because it can eliminate injection site abscesses in carcasses at the time of meat harvest.