The colour discrimination of 15 subjects manifesting senile macular degeneration was investigated, over a wide range of illuminances, using the Farnsworth-Munsell 100-Hue test and Panel D-15. Ten subjects of similar ages with normal colour vision were investigated concurrently to provide a control group. Colour discrimination was shown to deteriorate with decreasing illuminance this being more marked for the subjects with senile macular degeneration than for the normal subjects. It is demonstrated that the FM 100 is the preferred test for assessment of colour discrimination loss in senile macular degeneration with early visual acuity loss. The Panel D-15 is more useful as acuity loss becomes more marked.