The authors report electroretinogram (ERG) data from the initial clinic visit of 39 patients with central retinal vein occlusion (CRVO). No patient had signs of neovascular complications or had received treatment at the time of the ERG examination. Area under the receiver operating characteristic (ROC) curve was used to compare effectiveness of the 4 ERG parameters (Rmax, Log K, b/a wave ratio, and 30 Hz implicit time) in separating those patients who went on to iris neovascularization from those who did not. Rmax is the maximum saturated b-wave amplitude and Log K is the half saturation constant of the Naka-Rushton curve fit to the intensity response data. Discriminant scores, derived using multiple discriminant analysis, were calculated for the total patient groups, CRVO eye alone, and intereye difference. These scores also were compared with the four individual ERG parameters using ROC analysis. Parameters based on amplitude of ERG response, Rmax, and b/a wave ratio are as effective predictors of neovascular response as those interpreted as indicators of retinal sensitivity, such as 30Hz implicit time or Log K. The authors present evidence that loss of b-wave amplitude is not necessarily associated with irreversible loss of inner retinal function.