BRAZIL'S election of a civilian president, Tancredo Neves, after two decades of military rule, is an achievement of great promise. The passage from authoritarian government to democracy is always difficult, but the Brazilian example is unusually interesting. The generals had originally intended to steer the election to a civilian member of their own party, but the party split over the choice of a nominee. The limits on speech, the press and assembly have been left very wide during this process, and it rapidly become clear that the opposition candidate, Mr. Neves, commanded far wider public support. The generals saw the direction that events were taking and accepted it. Although the election yesterday was indirect, through an electoral college, there is every reason to think that a popular vote would have turned out the same way.

The first necessity of the new government when it takes office in March will be to manage the enormous wave of hope and expectation that this transition is generating. Brazil has been through a dire recession over the past four years in its struggle to carry its foreign debts, but its response has been unexpectedly successful. Exports have risen at a phenomenal rate, and the national economy is now beginning to grow again. Brazilians' high expectations of the new government can contribute to the next stage of this remarkable national effort, but to keep them focused on the main job will require unusual leadership. So far, all of the hard decisions in Brazil's adjustment have been made by people who had to answer to no one but themselves. Now policy is going to be in the hands of an elected government -- a better way to do it, but more difficult. Mr. Neves is very likely to make economic growth his primary objective. It is useful for Americans to remember that the degree of his success will inevitably be influenced by the growth, or the lack of it, in the world's largest market here in the United States.

With the election of Mr. Neves, Brazil greatly strengthens the trend toward democracy throughout South America. The new government has more in its favor than the economic indicators alone. Although the Brazilian military regime was tiring after its long tenure, it departs voluntarily and in good order -- unlike, for example, the rancorous Argentine junta that collapsed a little over a year ago, defeated in the Falklands War and discredited by the atrocities it inflicted on its own people. Similarly, whatever challenges await Mr. Neves, he will not be confronted with the kind of adversary that a strong and anti-democratic labor movement constitutes in Argentina. The turn to elected governments in both of those countries will now contribute to the stability of each of them. Who's ext? How about Chile?

There was much celebration in Brazil yesterday. Brazilians -- and their friends -- had much to celebrate.