A quantitative psychophysical and electroretinographic assessment of severely amblyopic human eyes revealed no electrophysiological retinal analogue of the psychophysical deficit, when objectively refracted. Electroretinograms to pattern and uniform field flicker were normal in all but one amblyope. In this amblyope, although the electroretinographic deficit was uncorrelated with the psychophysical deficit, the reduced amplitude of the pattern-evoked response was also seen in the second harmonic component to uniform field stimulation. The deficit for each stimulus was only present at high signal levels. The similarity of the pattern evoked response and the second harmonic response to uniform field stimulation in normal and amblyopic eyes suggests a similar underlying process.