Twenty one normal foaling Arabian mares were used in the present work. The alterations in the cells of vaginal smears and plasma progesterone profile were recorded during some reproductive phases in mares. There was an elevation in percentage of cornified cells and values of total leukocytic infiltration accompanied with the similarity in percentage of both small and large nucleated squamous cells were observed during puerperium. The relative increase in percentage of cornified cells, in addition to the similarity in percentage of both small and large nucleated squamous cells and the sharp decrease in values of total leukocytic infiltration were observed when the plasma progesterone concentration was sharply dropping during the 1st and 2nd postpartum estrus. The percentage of nucleated small squamous cells and values of total leukocytic infiltration, as well as the plasma progesterone concentration was increased during the 1st luteal phase, early stages of pregnancy and prolonged diestrus. The most important criterion predicting the mid and late stages of pregnancy are the increase in values of total leukocytic infiltration accompanied with the similarity in percentage of both small and large nucleated squamous cells which relatively enlarged in their size , meanwhile there was a non-significant variation in plasma progesterone levels with advancement of gestation.