Sao Paulo — Dressed in a multicolored T-shirt and designer jeans, Rita de Melo Dias is windowshopping in one of Sao Paulo's modern shopping malls.
''See those jeans?'' she asks. ''That's the kind we make at my plant, but I thought they were all exported. I guess there's a market for them right here in Brazil, too.''
Indeed, there is. Brazil's blue-jean industry is the second largest in the world. Its blue-jean sales this year will top $7.5 billion, with three-quarters of that amount sold in Brazil. The industry was built in just 12 years; its success reflects the rapid economic advances of many sectors of the Brazilian business community.
And Rita de Melo, secretary to a blue-jeans designer, reflects the changing complexion of young, middle-class Brazilians - a new consumer-oriented generation with money to spend that is very much like the urban middle class in many United States cities.
Many of Rita's contemporaries in the US, with whom except for language she would be comfortable, wear jeans made in Brazil, including some from Rita's plant.
''It's a dynamic, boom market,'' says a spokesman for the Associacao Brasileira de Jeans, the blue-jean industry's trade organization.
Yet that boom market, involving perhaps 60 million people, does not touch more than half the country's 125 million people. The number of have-nots in this sprawling country may well be growing faster than the haves, given the nation's population spiral.
For every Rita de Melo who is part of the Brazilian boom, there is a Susana Franco da Costa who is not part of it.
Just six blocks from Rita's air-conditioned shopping center of boutiques, designer clothing shops, and stores selling just about any consumer item that would be found in US shopping malls - Susana hunches over a stone basin, doing laundry in cold water.
The too-tight dress she wears is a hand-me-down from an older sister. The clothes she is washing are well worn, patched here and there.
''I've never been there,'' she confesses with a wan smile as she talks of the nearby shopping mall. ''I guess I'm scared to go, for everything will look too inviting. I am not sure I want to face that situation.''
Susana lives with her widowed mother in a ghetto-like favela on the edge of Sao Paulo, the heart of the industrial and agricultural region that has made Brazil the world's eighth-largest economic force.
She got a grade-school education, excelling in Portuguese literature, ''which I love,'' before her family's improving economic fortunes darkened with her father's passing 10 years ago. He managed on a small income to pay for schooling for his three daughters and had hopes of taking the family out of the favela into something better. Susana's face clouds as she talks of those dashed hopes.
For millions in Brazil, it is not a case of dashed hopes, but of no hope. This is the problem that mortgages Brazil's future.
Can this nation, Latin America's largest, really say it has ''made the grade, '' as a government candidate in the Nov. 15 voting took pride in proclaiming, with half its people outside this growth?
The millions of Rita de Melos in Sao Paulo, Rio de Janeiro, Belo Horizonte, Port Alegre, and elsewhere are testimony that the Brazil can provide promising futures for many who are upwardly mobil. Many young people are earning $5,000 or more yearly, a good salary here.
But half the population is like Susana Franco, either unemployed or underemployed (Susana works in a shoe factory part-time). Many of these people live on the edge of society; some live completely outside the mainstream economy.
The question of whether Brazil can be ''making it'' when so many of its people are not haunts many of Brazil's industrial and government leaders. Newspapers and news magazines here regularly tell stories that touch on this theme.
Istoe, in one of its weekly issues, noted last month that infant mortality in urban ghettos and rural regions of the country is ''extremely high,'' particularly in the impoverished northeast.
And statistics issued in Brasilia in November showed that 30 million Brazilians - one-quarter of the population - are ''totally removed from the economy.'' These are people who generally receive no education, who live in inadequate housing, and dress in rags, and do not hold gainful employment.
How do they survive? How do they manage? ''Badly,'' says Banco do Brasil economist Helio Barbosa da Sousa. ''No . . . worse, they barely survive.''
There was a time a few years ago when Brazilian officials and others more or less wrote off this part of the population - holding that if the rest of Brazil was to advance it could not worry about these millions.
That is no longer the situation. Talk about the future to Brazilian officials now and they readily acknowledge that ''this problem has got to be solved,'' as planning minister Antonio Delfim Netto says.
''Not until it is resolved,'' says banker Barbosa, ''not until we assimilate those millions into the mainstream will we really have made it.''
Actually, the process of assimilation is going on. The numbers of people finding jobs in Brazil - even as world slackening economic activity takes a toll on the Brazilian economy - are growing. The jeans industry is a case in point.
The 350 companies making up the industry producing T-shirts and jeans have not laid off workers despite the recession. The jeans industry grew in 1982 and expects a 10 percent growth in 1983.
This pattern of growth is repeated in a number of other industries - aircraft manufacture, light industries such as cutlerymaking, arms manufacture, citrus growing and processing, and the petrochemical industry.
Perhaps more important, in terms of helping the poor, is the increasing awareness of the problem in Brasilia and Sao Paulo. More Brazilians seem to be determined to find ways of solving the problem of bringing the have-nots into the mainstream economy. At the moment, the best hope Brazil has appears to be continued economic expansion, which would put more Brazilians into the economy.
A case in point: Recently, Susana Franco went from part-time to full-time hours in her shoe factory as a clerk/secretary. Her salary will be roughly $2, 700 a year. Her stockroom job was taken over by two people, since the company is expanding.
''This is our hope,'' banker Barbosa says, ''that more and more people will become part of the economy year by year.''