This digest analyzes the definitions of disability in the Individuals with Disabilities Education Act (IDEA). It notes that, in order to be eligible for special education services under the act, the child must meet two criteria: (1) he/she must have one or more of the specific disabilities listed in the act, and (2)he/she must require special education and related services. Definitions of the following specific disabilities listed in the act are included: autism, deafness, deaf-blindness, hearing impairment, mental retardation, multiple disabilities, orthopedic impairment, other health impairment, serious emotional disturbance, specific learning disability, speech or language impairment, traumatic brain injury, and visual impairment, including blindness. Requirements under IDEA for multidisciplinary evaluation and the inclusion of students with disabilities in regular classrooms whenever possible are also briefly noted. (DB)