Cloprostenol-15-glycal is an analog of natural prostaglandin F2 alpha. It is prepared fully synthetically and is a basic substance of the veterinary medicament of firm name Glystrofan (chem. conc. Spolana, Neratovice, CSR). The effect of this substance was studied after intravenous application in double concentration on the blood cell count in experiment on rats. A significant decrease of erythrocyte count was observed in late sampling intervals especially after higher dose. A temporary elevation of leucocyte count occurred in white blood cell series. There was lymphocyte count elevation, while neutrophil count decreased. In the course of experiment a decrease of thrombocyte count occurred, especially after higher dose. Characteristic of described changes corresponds to that, which was observed by prostaglandins of series E. Changes in perifery blood cell count can be in agreement with the effect of cloprostenol-15-glycal on the production or influence of growth factors and on the proliferation of pluripotent hematogenic cells respectively.