AbstractThis review deals with (1) standardization of the dog karyotype by the classical and molecular approaches, (2) nucleolar organizer regions, constitutive heterochromatin and meiotic chromosomes, (3) fluorescence in situ hybridization, (4) chromosome painting, (5) numerical and structural chromosome abnormalities, (6) cancer cytogenetics, and (7) the application of fluorescence in situ hybridization to studies of dog cancer.