The m-sequence stimulation technique that has previously been described allows simultaneous recording of many local electroretinograms (ERGs). For topographical mapping of cone function in the central retina ERG traces from 61 retinal areas were recorded during a 4-min period in 20 normal volunteers and 4 patients with age-related macular degeneration, Stargardt's disease, choroidal atrophy, and polymyalgia associated with visual field loss. The local photopic luminance response was analyzed in each of the 61 areas. In the 2 patients with macular disease central defects were detected, in the remaining patients local defects were found outside the macular region. The method of multifocal ERG recordings provides the possibility of objective testing of visual fields when the outer retinal layers are affected.