As Nelson Mandela tours the United States, it is easy -- almost too easy -- for Americans to feel a smug sense of moral superiority to the apartheid policy that dominated South Africa for far too long and kept Mandela in jail. Less comfortable, but more important, is a candid appraisal of race relations in our own society.

That task has been attempted by an unusual group -- not a civil rights lobby, not a minority organization, but 90 chief executives of major corporations and universities who call themselves the Business-Higher Education Forum. Their report, ''Three Realities,'' drew less attention than it deserved when published earlier this month.

What are the three realities they see? The first is that many minority-group members are succeeding. The black middle class has tripled in size in a generation. More than 40 percent of working-age blacks now are middle class. Nearly half own their own homes. Three years ago, about two out of five black and Hispanic families had incomes over $25,000.

The second reality is that another third of America's minorities live on the margin, with such limited skills and so little education they must scramble to survive. As the report says, ''They are falling behind economically and seem to be virtually invisible to our policymakers. ... The families of most unskilled workers qualify for little public aid. Many have no health insurance, but they do not qualify for Medicaid.'' Food stamps and unemployment programs rarely reach them.

The third reality is the one most of us would choose to ignore: the persistence of poverty for three out of 10 minority citizens, many of them trapped in an underclass plague of drugs, delinquency and broken families.

The executives found a vivid way to describe the fateful balance in this nation. In the 30 minutes they estimate it will take to read their report, about 250 people will become Americans -- 220 born here and 30 immigrants. ''In that same 30 minutes, more than 160 young people in the United States will make personal decisions that will affect them for the rest of their lives. Their families, their communities and the entire nation will also live with the consequences.

''Nearly 50 will drop out of school; 85 will commit a violent crime against another human being; 27 teenage girls will give birth, 16 of them out of wedlock.''

As successful executives, the authors, led by Steven C. Mason, president of the Mead Corp., and Clifton R. Wharton Jr., former president of Michigan State University and now head of the nation's largest private pension fund, are not satisfied to describe the problem and then walk away. They have met already with three members of the Cabinet and key congressmen as well as with their counterparts in the business and academic worlds. Their agenda suggests some things Americans can do here when we finish applauding what Mandela has done there.

For those on the margin and those who are not making it at all, they suggest restoring public-employment and training programs to the equivalent of their 1980 budget levels. While most of us were being lulled with claims that the ''social safety net'' was being kept intact, those funds were cut by more than half -- from $8.5 billion to $4 billion -- and further diminished by inflation.

They also call for full funding of Head Start and its follow-on programs in the elementary grades, which now reach only one-third of the eligible youngsters. They want grants, instead of loans, for low-income students in the first two years of college. And they want families of all low-income students to be told when they enter the seventh grade that if they buckle down to schoolwork, their college costs will be guaranteed.

In their own bailiwicks, the corporate and college presidents strongly endorse affirmative-action programs and point to model outreach programs that seemingly do bring more blacks and Hispanics onto campuses and into career-track jobs. The decline in the percentage of minority enrollments of the past 10 years is neither acceptable nor inevitable, they say.

And they have something important and unusual to say about the ways in which big businesses -- including universities, which often are the largest employers and purchasers in their communities -- can help small businesses owned and run by minorities get started and survive. The tools include capital investment, counseling and awarding of franchises. One Chicago bank they cite has helped create job-training and placement programs for 3,000 people, given advice to 1,000 would-be entrepreneurs and assisted the start up of at least 70 new businesses -- and made money in the process.

What these executives are saying is: The challenge is there, but so are the tools to meet it. When the applause for Mandela stops, the test will be how many turn their hands to these tasks.