The Court first considered whether the plaintiff was disabled as defined in the ADA. The relevant section is 12102(2)(A) "a physical or mental impairment that substantially limits one or more of the major life activities of such individual." Before discussing whether the plaintiff met this test, the Court indirectly addressed the lower courts' attempts to narrow the ADA by over restrictive readings of its provisions. The Court noted that when Congress uses well-established terms, it intends that they be construed in accordance with established interpretations, and that this is explicit in the ADA: "Except as otherwise provided in this chapter, nothing in this chapter shall be construed to apply a lesser standard than the standards applied under Title V of the Rehabilitation Act of 1973 (29 U.S.C. § 790 et seq.) or the regulations issued by Federal agencies pursuant to such title."

The Court found that the plaintiff had to show three things: (1) that HIV was a physical impairment; (2) that it affected some major life activity; and (3) that this limitation be substantial. All of the judges' opinions accepted that HIV infection, irrespective of the symptoms, is a physical impairment as contemplated by the ADA. The Court's opinion goes into unnecessary length on the technical details of HIV infection. (Although these are not necessary to its conclusions, most courts cannot resist the temptation to lift scientific jargon from the briefs before them, irrespective of whether it is relevant or even in evidence.)

The Court's analysis is complicated by the politics of HIV-related disability litigation. The position of AIDS rights organizations is that asymptomatic HIV infection has no effect on the infected person's ability to carry on day-to-day life activities. This position is incompatible with the requirements of the ADA-if there is no effect on a major life activity, then the physical impairment is not a covered disability. However, conceding that asymptomatic HIV infection does have an effect on major life activities means that employers and others might have a right to know HIV status if its effect on major life activities might endanger others. Plaintiff finessed this by focusing on her ability to bear children.

Defendant argued that reproduction, as the court termed it, was not a major life activity as contemplated by the ADA. Defendant's theory was that the ADA required that the life function affected be of a public, economic, or daily character. (Although not put in these terms, this essentially means that the disability be related to the claimed discrimination.) In what may be the most significant part of the opinion, the Court found that a major life activity need not be economic, public, or recurrent, that the key word was major, and that reproduction was a major life activity. This analysis potentially overrules many circuit cases that used a very narrow definition of major life activity.

The third prong of the ADA definition is whether the impairment affects the major life activity. Plaintiff argued that the chance of infecting a partner and passing the infection on to her children affected the major life activity of reproduction. The Court could find no guidance on this issue, but agreed that these factors certainly affected a person's decision to have children. The Court held that this satisfied the ADA requirements, making her HIV infection a covered disability.