The frequency and distribution of dog leucocyte antigens (DLA) class II -DQA1, -DQB1 and -DRB1 alleles were determined for 25 American Kennel Club (AKC) registered dog breeds, representing 360 dogs from each of the seven major performance categories. Six to twenty-eight (average n=11) dogs were studied per group, with the exception of the Akita dog (n=94). All dogs were unrelated with no common grandparents based on AKC pedigree records (F-value <0.125). DLA class II allelic diversity was broad across breeds; 31/61 published DLA-DRB1 alleles, 11/18 published DLA-DQA1 alleles and 31/47 published DLA-DQB1 alleles were found among the 25 breeds. However, allelic diversity was severely limited within a breed. Seventeen of the DLA-DRB1 alleles were each found in only a single breed, and only seven alleles were shared by seven or more breeds. DLA-DRB1*00101 and DLA-DRB1*01501 were shared by 16 and 19 breeds, respectively. DLA-DQA1*00101 and DLA-DQA1*00601 alleles were shared by many breeds. The Rough Collie (DLA-DQA1*00901), English Setter (DLA-DQA1*00101) and Scottish Terrier (DLA-DQA1*00101) were monoallelic for DLA-DQA1. Eleven DLA-DQB1 alleles were each found only in a single breed and only seven alleles were shared by six or more breeds. DLA-DQB1*00201 and DLA-DQB1*02301 were shared by 17 and 18 breeds, respectively. Forty per cent of dogs typed were homozygous at DLA-DRB1, 52% at DLA-DQA1 and 44% at DLA-DQB1. Nine new DLA class II alleles were identified; three for DRB1 and six for DQB1. Comparison of our study of North American purebred dogs to previous European DLA surveys showed a similar use of common alleles consistent with known founder effects. However, more alleles were detected in European breeds, compared to their North American descendents, indicating that additional DLA class II diversity was lost when European breeds were established in North America.