The Listing of Impairments describes, for each major body system, impairments that are considered severe enough to prevent a person from doing any gainful activity (or in the case of children under age 18 applying for SSI, cause marked and severe functional limitations). Most of the listed impairments are permanent or expected to result in death, or a specific statement of duration is made. For all others, the evidence must show that the impairment has lasted or is expected to last for a continuous period of at least 12 months. The criteria in the Listing of Impairments are applicable to evaluation of claims for disability benefits or payments under both the Social Security disability insurance and SSI programs. Part A

This section of the Listing of Impairments contains medical criteria that apply to adults age 18 and over. The medical criteria in Part A (Adult Listings) may also be applied in evaluating impairments in persons under age 18 if the disease processes have a similar effect on adults and younger persons.

Part B

This section of the Listing of Impairments contains additional medical criteria that apply only to the evaluation of impairments of persons under age 18. Certain criteria in Part A do not give appropriate consideration to the particular effects of the disease processes in childhood, i.e., when the disease process is generally found only in children or when the disease process differs in its effect on children and adults.

Additional criteria are included in Part B (Child Listings) and the impairment categories are, to the extent possible, numbered to maintain a relationship with their counterparts in Part A. In evaluating disability for a person under age 18, Part B will be used first. If the medical criteria in Part B do not apply, then the medical criteria in Part A will be used.

The criteria in the Listing of Impairments apply only to one step of the multi-step sequential evaluation process. At that step, the presence of an impairment that meets the criteria in the Listing of Impairments (or that is of equal severity) is usually sufficient to establish that an individual who is not working is disabled.

However, the absence of a listing-level impairment does not mean the individual is not disabled. Rather, it merely requires the adjudicator to move on to the next step of the process and apply other rules in order to resolve the issue of disability.