Electroretinograms (ERGs) were obtained from pigmented and albino rats to step luminance changes of an unpatterned TV screen. Surround luminance was increased until the ERG became small and focal. In pigmented rats the ERG at on was positive, earlier, and about twice the amplitude of the negative ERG at off. All pigmented rats had pattern ERGs-0.5 cycles/deg in dark agouti rats and an octave less in hooded rats. Implicit peak times were similar to that of the sum of on plus off focal ERGs from the same animals (85 ms). In albino rats off responses were more like on. The resultant sum was consequently small. Both peak times were similar and did not move earlier than 120 ms as surround luminance increased. Pattern ERGs could not be recorded from albinos at any spatial frequency or surround luminance. These pigmented rat ERGs seem to have two major components. One follows luminance linearly; the other is a fully rectified nonlinearity with about one-third the amplitude. The albino rat retina apparently lacks the latter component. These deficiencies may occur in albinos of other species and be associated with their visual system abnormalities.