When the president signed the Americans with Disabilities Act (ADA) this week, basic civil rights protections were extended to the 43 million disabled Americans as they were to racial minorities in 1964. The bill's enactment was a tribute to strong bipartisan national leadership.

But the civil rights goals of the ADA -- to bring disabled persons into the mainstream of American life -- are likely to be frustrated unless the other components of the nation's disability policy are also addressed: income and in-kind (e.g., medical) assistance programs and skill-enhancement programs such as education and vocational rehabilitation.

The two most important disability income programs are the Social Security Disability Insurance (SSDI) program and the Supplemental Security Income (SSI) program. Financed from Social Security taxes and general revenues, these programs paid out $38.3 billion to more than 5 million disabled persons and their families in 1989. They also determine a disabled person's eligibility for a variety of other benefits, such as health care under the Medicare and Medicaid programs.

While these programs are an important part of the nation's safety net for persons with disabilities, their eligibility requirements are a major reason why many disabled persons do not work. To be eligible for benefits, SSDI and SSI applicants must demonstrate that they have a medical condition that renders them unable to work, or have a condition that will result in death. Until recently, even the slightest hint of earning capacity rendered a person ineligible for further benefits.

This state of affairs is rooted in policy formulated in the '50s, which assumed that a disabled individual's condition was so hopeless that future prospects for employment were impossible.

In the years since, improvements in medical rehabilitation, the development of new technologies and changing expectations have broadened opportunities for independent living and employment. Yet only one-fourth of working-age Americans with disabilities are employed full-time today. Very few SSDI or SSI recipients return to work and leave these programs.

To address this problem, Congress has amended the SSDI and SSI programs during the past 10 years to enable persons to return to work without the precipitous loss of income and in-kind benefits.

However, eligibility for program benefits continues to be based on the determination that a person is totally unable to work because of a medical condition. This creates an inherent and self-fulfilling work disincentive that cannot be addressed adequately through incremental measures. After demonstrating so earnestly that they are disabled enough to qualify for SSDI or SSI, many disabled persons become convinced that they are too disabled ever to work. Those who do not believe this are hesitant to risk losing their eligibility through employment, even if they are assured that they will probably be able to regain eligibility if necessary.

In stark contrast, disabled persons in several European countries are eligible for the assistance they need regardless of employment status. They therefore have no fear that they will lose important support benefits if they decide to become gainfully employed.

What makes income and in-kind assistance such an important part of our disability policy is that it is the most heavily financed component. Economic incentives and disincentives do more to shape individual decision making than all the regulatory machinery that the ADA can muster.

As for skill enhancement, major strides have been made to mainstream the education of disabled children through the Education for All Handicapped Children Act. We must now improve opportunities for college and graduate-level training for persons with disabilities so they may participate in professional-level jobs. Because of their functional limitations and the high costs associated with their needs, disabled persons require professional-level employment even more than non-disabled persons.

The ADA has offered Congress and the administration an opportunity to face the changing needs and aspirations of an increasingly politicized disabled population. The same political willingness must now be extended to the other components of the nation's response to disability.

Gerben DeJong is director of the National Rehabilitation Hospital Research Center. Andrew I. Batavia is the center's associate director for health services research.