Survey data on roadway superelevation, curvature, and grade collected at the sites of fatal rollover accidents and at comparison sites in New Mexico and Georgia were analyzed to determine the effect of grade on superelevation after adjustment for curvature. These adjusted data were then used to determine the effect of superelevation on accidents. After adjustment for curvature, it was found that in comparison with flat roadway sections (grade+ 2.5 to-2.5 percent) sections with grade (greater than+ 2.5 or less than-2.5 percent) had less superelevation. After adjustments for both curvature and grade, fatal rollover accident sections were found to have less superelevation than comparison sections. Inadequate superelevation presents a risk that should be eliminated from the roadway system.