THE QUESTION is not whether the South African regime is admirable, or whether its practice of racial apartheid is, by any civilized standard, anything but repellant. They are not. The International Monetary Fund is to vote today on a loan of $1.1 billion to South Africa, and many Americans, including some in Congress, believe that the loan ought to be denied. But the real question is whether to continue a worldwide monetary system that, necessarily, includes some pretty unattractive governments.

If American moral approval becomes necessary for membership in the IMF, the IMF will not last very long, and the world will lose one of its more effective economic stabilizers. The right choice for the American representative is, uncomfortably, to let the loan pass.

South Africa has contributed to the IMF in the past and, under the rules, has a right to draw on it now. There have been suggestions, here and in Europe, that since the IMF often attaches conditions to its loans, it should proceed here to commit the South African government to accelerate its exceedingly modest relaxation of apartheid. Unfortunately, that tactic isn't quite so promising as it looks. The IMF makes many kinds of loans and, as the practice has evolved, the conditions are kept in proportion to the help the borrower needs. South Africa is asking for a routine loan to finance a temporary trade deficit. By the IMF's standard usage, approval would be automatic. To try to attach conditions of broad political significance to that kind of loan would mean singling out South Africa for a kind of treatment given to no other country.

Over the years, the IMF has been profoundly, and sometimes crucially, helpful to countries of great importance to the United States. Its help will be essential, for example, to Mexico in overcoming the crisis there. But the IMF is founded on the reality that financial distress in one country -- regardless of its moral standing -- quickly spreads to others. That's why the IMF is open to any country. It has often made loans to some of the world's least appealing governments. Argentina, Rumania, Zaire, Vietnam and China are all repressive governments, in varying degrees.

Why help any? To preserve the balance of the world trading and financial system of which they are part. There is some danger that Congress will be tempted to use the South African loan as a reason, next year, to deny further American support to the IMF. But if the IMF's resources begin to fall short, South Africa will suffer less than the poorer countries--Jamaica is one important current example. They all belong to the same system, and South Africa is not the most vulnerable among them.