Description: The objective of this study was to determine a baseline vaginal pH value for clinically healthy dairy cattle and to examine whether this value varies as a function of days in milk (DIM) or parity. One hundred and seventy one healthy Israeli Holstein-Friesian breed cows, heifers and first calf heifers, located on one farm were screened on the same day for vaginal pH values by intravaginal insertion of a pH strip. The mean pH value for cows, heifers and first calf heifers was 7.35, 7.58 and 7.48 respectively; the median value was 7.50 for all groups. DIM did not significantly influence vaginal pH values in the examined population. In addition, vaginal pH values were measured in 18 healthy cows and nine healthy first calf heifers of Israeli Holstein-Friesian breed, on another farm, during the periparturient period. While the mean pH values remained stable for cows before and after parturition at around 7.50, in the 1st calf heifer group, the mean pH was 7.25 one week before parturition; the value increased to 7.75 the week following parturition and finally stabilized at about 7.50. Results show that regardless of the periparturient period, cows and heifers tend to have more variable vaginal pH than first calf heifers and that vaginal pH values tend to be more acidic in cows. These differences may contribute to the increased susceptibility of first calf heifers to vaginal infections such as bovine necrotic vulvovaginitis