The age-related variation of the fluorescence of the human eye lens was calculated from published data for lenticular absorbance. Only the nucleus was assumed to be involved. Simplifying assumptions for nuclear geometry yielded axial point-by-point data of absorbance for the exciting and fluorescent beam intensities. The resulting fluorescence profiles and their variation with age were computed. The model was tested on two assumptions: yellowing of the lens involves a pigment (a) already present at, or (b) one accumulating from, birth. Agreement between theory and experiment follows from hypothesis (b), and supports an earlier suggestion that the lens may yellow owing to a lifelong exposure to light.