I examined sexual dimorphism in the lacertids Gallotia atlantica atlantica and Gallotia atlantica mahoratae from Lanzarote and Fuerteventura Islands, respectively. Mean body size was smaller in G. a. mahoratae than in G. a. atlantica. Sexual size dimorphism was greater in G. a. atlantica than in G. a. mahoratae, but relative size of several morphological traits was not different between the two populations. In both subspecies, head and body traits scaled to SVL, with head size of males having a positive allometry, indicating a disproportionate increase of this trait with the increase in body size. Relative size in hind-limb length was greater in males than in females in G. a. atlantica but not in G. a. mahoratae.