The purpose of the present study was to evaluate the effects of maternal protein and energy restriction during lactation on the bodyweight and skull dimensions of pups at weaning. At parturition, Wistar rat dams were randomly assigned to the following groups: (i) control group (C), free access to a standard laboratory diet containing 23% protein; (ii) protein-energy-restricted group (PER), free access to an isoenergetic, protein-restricted diet containing 8% protein; and (iii) energy-restricted group (ER), restricted amounts of a standard laboratory diet. The dimensions of excised pup skulls were measured directly using pre-established anatomical points. Morphometrical analysis of the skulls showed that most of the measurements in the ER and PER groups were significantly lower than in the control group, with the greatest reductions occurring in the PER group. These results show that protein and energy restriction during lactation have an important influence on pup skull development.