Quantitative data (numbers of neurones and glial cells, total volumes, internuclear volumes) were obtained during normal development and after bilateral and unilateral enucleation at birth in the dorsal lateral geniculate nucleus (LGNd) of the mouse, at 5, 10, 30, 60, and 180 days postnatal. During normal development there is a neuronal loss of about 30% up to 30 days, at which age the total number of neurones stabilises at around 17,000. Glial proliferation and an increase in the volume of LGNd continues at least to 180 days. More severe degenerative effects were found after bilateral than after unilateral enucleation. At 180 days, bilateral enucleation leads to a neuronal loss of 27% compared to the controls, with a glial deficit of 53% and a decrease in the volume of LGNd of 57%. Degenerative effects were very different in LGNd contralateral or ipsilateral to enucleation in monocularly enucleated mice, due to the extensive crossing of the retinal fibres. At 180 days, we found a deficit of 10% in the numbers of neurones and glial cells, in the ipsilateral LGNd compared to normal: the volume of LGNd was slightly less (3%) than in controls. The contralateral LGNd after unilateral enucleation behaved like LGNd after bilateral enucleation until 60 days. At 180 days, some minor modifications were found, showing an additional neuropil decrease of 13% and an additional neuronal loss of 6% in the bilaterally enucleated LGNd compared to the unilaterally enucleated contralateral LGNd. The time-course of degeneration both after bilateral and unilateral enucleation was discussed.