As Grif said, diploid is two sets of chromosomes - one set from the male and one from the female. A few species of frogs are considered polyploidy or having more than one pair. It is likely the diploid represents the most ancient of the species within the genus. Among frogs, the genus Xenopus (African clawed frogs) has the most diverse of chromosome numbers - there are species that are diploid (2 sets); tetraploid (4 sets); octoploid (8 sets) and dodecaploid (12 sets).

Often times, identification of a particular species can be extremely difficult due to "cryptic species" - a group of species which satisfy the biological definition of species—that is, they are reproductively isolated from each other—but whose body characteristics are very similar (in some cases virtually identical). The only way to tell them apart is by advertisement call and analyzing the DNA. A great example concerns the two species of gray treefrogs of North America - they are physically identical, their call and DNA are different. Hyla chrysoscelis is diploid (call is of higher pitch) and H. versicolor is tetraploid (lower pitch).

Another detailed study of cryptic species is on the sand frogs of Southern Africa (genus Tomopterna, also known as "pyxie frogs" and a relative to the African bullfrog).