Eighty-six new microsatellite loci were developed for European hazelnut (Corylus avellana L.) by screening two genomic libraries enriched for dinucleotide repeats. The loci, 73 developed from a GA-enriched library and 13 from a CA-enriched library, showed a high level of polymorphism in 50 accessions. The number of alleles per locus ranged from five to 21, with a mean of 10.55. Mean values for expected heterozygosity, observed heterozygosity, and polymorphism information content were high, averaging 0.76, 0.69, and 0.73, respectively. In a mapping population, loci segregated 1:1, 1:2:1, and 1:1:1:1. Segregation distortion and null alleles were observed at some loci. Eighty-one of the 86 loci were assigned to linkage groups. A neighbor-joining dendrogram reflected great diversity among the 50 accessions and showed clustering by geographic origin.