The effects of perinatal undernutrition on the number of neurons and apoptotic cells of the locus coeruleus (LC) of female and male rats at postpartum days 7, 12, 20, 30 and 60 were studied. Undernutrition reduces the number of neurons in both sexes without affecting cell death, as indicated by the ratio of apoptotic cells to neurons. The data suggest that in the undernourished groups lower rates of neurogenesis and proliferation (neurogenetic/proliferation rates) might avoid these animals achieving the number of LC neurons as in the control subjects. Although food restriction in both sexes apparently provokes the loss of cells, the effect does not appear to be equal in females and males, as shown by post weaning food rehabilitation. The results suggest that severe food deprivation may interfere with the ontogenetic processes underlying neuronal differentiation of the LC. Morphological damage in the LC due to undernutrition might alter the physiology of sexual and/or feeding behaviours in which this structure is implicated.