The Social Security Act (Act) defines 'disability' as the 'inability to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which can be expected to result in death or which has lasted or can be expected to last for a continuous period of not less than 12 months . . . .' A party is considered disabled if she had medical impairments so severe that she was unable to perform her past work or, considering her age, education, and work experience, she is unable to perform any other available work. D has established a five-step evaluation process for determining whether a person is disabled. Step one determines whether the claimant is engaged in 'substantial gainful activity.' If she is not, the decision maker proceeds to step two, which determines whether the claimant has a medically severe impairment or combination of impairments. That determination is governed by the 'severity regulation' at issue in this case. The severity regulation provides: 'If you do not have any impairment or combination of impairments which significantly limits your physical or mental ability to do basic work activities, we will find that you do not have a severe impairment and are, therefore, not disabled. We will not consider your age, education, and work experience.' P has the burden to prove disability. P applied for both Social Security disability insurance benefits and SSI benefits. P alleged that she was disabled by an inner ear dysfunction, dizzy spells, headaches, an inability to focus her eyes, and flat feet. D determined that P was not disabled. At a hearing, the ALJ found that multiple tests failed to divulge objective clinical findings of abnormalities that support P's severity of the stated impairments. The ALJ found that P was pursuing a 'relatively difficult' 2-year course in computer programming at a community college and was able to drive her car 80 to 90 miles each week. The Appeals Council denied review. P appealed. The case was referred to a Magistrate, who concluded that D's determination was supported by substantial evidence. The District Court affirmed the denial of P's claim. The Ninth Circuit held that 'both medical and vocational factors [i. e., age, education, and work experience] must be considered in determining disability.” The court concluded that 'the legislative history does not suggest that Congress intended to permit findings of non-disability based on medical factors alone.' The Supreme Court granted certiorari.