Clementine mandarins, is a very important fruit group due the production of high quality fruits that can be seedless as consequence to their sexual self-incompatibility. In this study, the self-compatible/incompatible status of 40 clementine mandarins provided by the Cukurova University collection was determined by histological analysis. For this purpose, self-pollinations were performed and pistil samples were taken 3, 5, 7, 9, 11, 13, 15 and 20 days after pollination. All samples were fixed in FPA70 solution and stored at 4 degrees C. Pistil samples were stained with aniline blue and observed by fluorescence microscope following the staining and squashing. All pollen tubes of the genotypes arrested growth in the upper or middle part of style and none reached the base of the style. As a result, all the 40 clementine cultivars tested have been identified as self-incompatible.