In 1994 and 1995, this variable is part of the Disability Supplement (NHIS-D) that collects information on disability. NHIS-D included two household interviews: in Phase I all members of sample families were screened for any indication of disability; in Phase II persons with any indication of disability were followed-up for additional information. Phase I includes sensory, communication, and mobility problems; health conditions; activities of daily living and independent activities of daily living; functional limitations; mental health; services and benefits; special health needs of children; early child development; education; relationship to respondent; and perceived disability. Phase II includes four Disability Followback Survey (DFS) questionnaires: one for children, one for adults, one for elderly persons (69 years of age and over) without any indication of disability (also called the Supplement on Aging or SOA; only in 1994), and one for persons with a history of polio.

The Field Representative's Manual for 2001 forward defined Cerebral Palsy as "a disability resulting from damage to the brain before, during, or shortly after birth and outwardly manifested by muscular in coordination and speech disturbances." This definition was not routinely shared with respondents.

From 1997 forward, cerebral palsy was also included in the survey as an example of "other developmental problem" (i.e., "other" relative to "mental retardation") when information was collected on the conditions or health problems that limited an individual's activities (CLIMOTHDEV). Information was collected separately on whether a sample child was ever diagnosed as having "other developmental delay" (i.e., "other" relative to "Mental Retardation" and "ADD/ADHD") (ODDEV).