Sullivan v. Zebley, 493 U.S. 521 (1990), was a landmark decision by the United States Supreme Court involving the determination of childhood Social Security Disability benefits. In the decision, the Supreme Court ruled that substantial parts of the Supplemental Security Income program's regulation on determining disability for children were inconsistent with the Social Security Act, particularly the statutory standard of "comparable severity". The suit highlighted what some felt was the need for a step in the evaluation of childhood disability claims that would be akin to the functional evaluation considered in many adult claims. It resulted in the addition of a consideration of functioning, and not merely medical severity, in children's SSI claims. The decision was rendered on February 20