Abstract: By means of isozymes analysis, the authors studied the peroxidase and esterase patterns of mature needles of the female and male individuals of four species:Eastern Redceder (Sabina virginiana (L.) Ant.),Chinese Juniper (Sabina chinem (L.) Ant.),Needle Juniper (Juniperus rigida Sieb. et Zucc.) andCommon Juniper (Juniperus communis L.).The results of our experiments showed that there are clear differences both in zymogram numbers and patterns between the female and male individuals of each species. There seems to be a close relationship between sex expressions and isozymes, which may be considered as an indication of sex differentiation in different tree species.