IN THE CREAM-COLORED corridors of Howrey & Simon on Pennsylvania Avenue, an army of 120 legal assistants organizes, indexes and computerizes hundreds of thousands of documents generated by massive antitrust cases handled by the firm's 100 lawyers.

At the Federal Energy Regulatory Commission, a paralegal for he Houston-based firm of Baker & Botts stalks the halls searching for news to be passed on to the energy producers who are the firm's clients. There on North Capitol Street, where decisions mean millions for Baker & Botts clients, the paralegal is the firm's eyes and ears.

And in small legal services offices scattered throughout the country, paralegals, with the approval of federal law, help poor people get their food stamps and social security payments, as well as medicare, medicaid and unemployment checks. They are the advocates for the poor in coping with the tangled bureaucracy of federal benefit programs.

Their profession is only about 10 years old, but paralegals are now a fixture in the law business. Once overly protective of their role, lawyers have increasingly recognized that not everything they do requires a law school diploma, that paralegals can do much of the work once delegated to higher-priced young lawyers, and that paralegals can be valuable -- and money-making -- additions to a law firm.

The Bureau of Labor Statistics roughly estimates that 21,000 paralegals were working in the nation's law firms and local, state and federal government offices as of 1977.

The members of this new work force range from college graduates who see paralegal jobs as an entry to law school to women who decide to reenter the employment market after raising a family.

The starting salary for Washington paralegals is $12,000 to $14,000, according to The Paralegal Stitute, a private school that trains more than 150 paralegals a year in the metropolitan Washington area. salaries can exceed $20,000 with experience, overtime and holiday bonuses. At Baker & Botts, paralegals, along with secretaries and messengers, were given a share of a multi-million-dollar decision won by the firm's lawyers in 1978.

In many ways, however, paralegals are still looking for their place in the law business. They stand somewhere between clerical workers and lawyers, but their exact role is often clouded. The American Bar Association wonders if they should be certified, like paramedics. And as the paralegals grow in number and sophistication, they inevitably find themselves confronted with sensitive ethical questions about what they can and cannot do on the job.

Wald, Harkrader & Ross in Washington, which employs 35 full-time paralegals to assist 70 lawyers, recently published a thick Manual for Legal Assistants, which begins with a summary of what the paralegal can do: proofread, digest documents, draft simple pleadings and help interview witnesses in preparation for trial, among other things. The next page opens a thorough discussion of ethical considerations for paralegals.

"Most paralegals thought legal ethics didn't apply to them, but they were dead wrong," said David T. Austern, of the Washington firm of Goldfarb Singer & Austern. Austern teaches legal ethics for paralegals at George Washington and Georgetown universities.

The ABA code of professional responsibility says lawyers must make sure their employes abide by the code's ethical rules -- and that includes paralegals. And the Wald Harkrader manual notes that although paralegals are not subject to sanctions -- since they are not members of the bar -- the attorneys who supervise them could face disciplinary action if the paralegal acts unethically.

The ABA has addressed some elementary questions about paralegals, such as whether they can use business cards (yes), or have their names on firm letterheads or doors (no). What gets tough are the gray areas between giving information or giving advice. The code says in effect that when the independent judgements of a lawyer is required, the paralegal cannot give advice. The question, of course, is what constitutes the judgement of a lawyer.

For example, Austern said, can a paralegal advise a taxpayer on how to make the most out of the law on capital gains? Can a paralegal advise a home buyer on a legal point in a sales contract -- something real estate agents do every day?

"It is my perception . . . that there are law firms and lawyers in this town who permit their paralegals to give legal advice which they may or may not be qualified to give, which raises serious ethical considerations," Austern said in a telephone interview.

Paralegal training, formal or informal, has become an issue of some concern.

The paralegal movement started in the late 1960s with the public interest effort to make legal services more available to the poor. As the caseload mushroomed, a system of non-lawyer representatives -- paralegals -- developed out of sheer necessity. Gradually, the economy -minded private sector, the law firms, the corporations and insurance companies, latched onto the idea.

The next development was the emergence of schools for paralegals. First, there was the Institute for Paralegal Training in Philadelphia, founded in 1970. Universities, colleges and junior colleges added paralegal training to their curriculums. Courses include basic techniques in legal research, fundamental legal principles, document preparations. Now, there are more than 300 such programs in the country, according to Aaron Crasner, the director of the Philadelphia Institute.

But paralegal school is not a prerequisite for the trade, and some firms, especially those with highly specialized practices, prefer to train their own legal assistants.

"I'm handling big economic cases and there is no real training ground for [a paralegal] other than here," said Samuel H. Seymour of Seymour & Dudley in Washington.

In 1975, a special ABA committee considered trying to certify legal assistants but decided to hold off. The committee suggested a national study to examine the role of the paralegal and to devise a way to measure competency. Two years later, the committee again put off the questionof certification and asked the ABA for funds for the study, but was turned down. As it stands now, the most the ABA has done is "approve" a 49 paralegal training programs.

"We've taken the position that it's premature to do any certification at this time. It's not well enough defined what a legal assistant or a paralegal is," said Robert S. Musklestone, the chairman of the ABA's standing committee on legal assistants.

The paralegals, meanwhile, want the ABA to keep its hands off.

"It's the old game of the mother profession trying to rein in the children," said Carol Ann Woods, the president of the 500-member National Capital Area Paralegal Association.

"Obviously they are trying to protect themselves," Woods said of the organized bar. "Paralegals are supposed to bring the cost of legal services down," she said. But if certification requires formal training, the costs would rise, Woods said.

Strict certification requirements could hurt public sector paralegals, said Robert D. Hoffman, deputy director of the National Paralegal Institute, a nonprofit organization that promotes the training and use of nonlawyers in public law areas. These paralegals, who range from migrant workers to bureaucrats, may not have the time or the money to spend in a paralegal school when on-the-job training is available, Hoffman said.