Olive (Olea europaea L.) is an important fruit crop, with many health promoting properties being continuously discovered. World demand for both the fruit and olive oil is increasing in pace and hence countries try to meet the demand by disseminating 1 or 2 productive and adaptive cultivars to different regions formerly dominated by local cultivars. This study was performed to investigate the level of diversity in a very productive and adaptive cultivar, Gemlik, which has started to dominate most of the olive growing regions of Turkey. Three different marker systems, namely microsatellites (SSR), RAPD, and AFLP, with 15, 20, and 3 primer combinations, respectively, could not detect any genetic variation among 60 olive cv. Gemlik specimens sampled from 5 different regions, except several rare and random polymorphisms. The results showed that the expanding cultivar most possibly belonged to the clones of a single tree and revealed 100% sample identity.