This paper deals with stomata strucutre in the Rubiaceae family. This family in the order Rubiales is the only one to show the stomata structure relationed to the subsidiary cells. Twentyeight individuals representing several forms, varieties and espécies of the genus Coffea were studied and the uniformity regarding that structure observed. It is possible that the stomata structure, studied in detail in this paper, is a good character to distinguish the Rubiaceae family. Analysis of the other genus wil be carried on in order to confirm the observations made in the genus Coffea.