A comparison of sensitivities to chromatic and luminance stimuli has been carried out in patients with a past history of optic neuritis. Patients were selected with differing degrees of stable residual visual deficits, and with marked interocular differences in sensitivity. Threshold contrast sensitivity was measured to sinusoidal luminance gratings and to chromatic red/green and blue/yellow gratings, all with the same spatial frequency of 1 cycle per degree. A psychophysical criterion was used to ensure that detection of the chromatic grating was determined only by its colour differences. When the difference between the sensitivity to luminance and chromatic gratings was compared between the more and less severely affected eyes of each subject, it was found that, overall, chromatic sensitivity was more severely impaired than luminance sensitivity in the disorder. Sensitivities to the red/green and the blue/yellow stimuli were found to be affected equally.