The objective of the current study was to determine the immunohistochemical distribution and density of prolactin containing cells in the pituitary of the female and male chickens during postnatal developing period after hatching for five months. The modified labelled avidin-biotin method with monoclonal mouse antihuman prolactin as a primary antibody was used to detect prolactin positive cells. At the end of each month, prolactin containing cells were identified in the pars distalis of the pituitary glands of chickens. The number of the prolactin positive cells were found to be increased depending on the monthly development period, while the reaction density was found to be decreased in all groups. Additionally, males had less prolactin positive cells than that of females.