The size, body conformation and skull shape of Roman dogs from the ‘Vila de Madrid necropolis’ site, where 1480 dog remains were recovered, are described in this paper to provide evidence of the morphometric variability of Roman dogs in Hispania Tarraconensis. The individualized and detailed morphometric analysis of 10 individuals shows that the proliferation and explosion of the morphological variability already documented in different regions of the Roman Empire (Italia, Gallia, Britannia, Pannonia) are also noted here. The presence of very different individuals in terms of their shape and size, similar to the differences that can at present be noted between Pekingese and Doberman dogs, has been documented at the site. The reasons for the appearance of this morphological variability within those territories that were part of the Roman Empire are also discussed. Copyright © 2015 John Wiley & Sons, Ltd.