Characterization of Turkish hazelnut cultivars and the genetic relationships among them were determined by Randomly Amplified Polymorphic DNA (RAPD) markers. Forty-three decamer primers produced a total of 241 clear and reproducible bands. The number of bands produced by primers was between 1 and 12 with an average of 5.7. Specific RAPD bands were associated with some cultivars. The high level of polymorphism corresponded to a high degree of genetic variation among hazelnut genotypes with Dice's similarity coefficients ranging from 0.477 to 0.941. The highest similarity coefficient was between 'Uzuninusa' and 'Kan' while the lowest was between 'Yassi Badem' and 'K-24-2' Cluster analysis of band profiles showed heterogeneity among genotypes from the same area of cultivation. The standard cultivar 'Tombul' and its selections '190' and '260' were not clustered together in the UPGMA dendrogram and their Dice's similarity coefficients with 'Tombul' were 0.745 and 0.696 respectively. The results indicated that 'Tombul' and its selections are different clones, and it appears that 'Tombul' is a commercial name given to a group of clones grown in the Black Sea region with similar appearance but showing minor differences.