The hottest law firm in town is one you've probably never heard of.

It is a mere five years and three months old. In an era of firms composed of hundreds of lawyers, it has just 10. But within the small, cloistered world of Supreme Court clerks and other law school graduates with impeccable credentials, Onek, Klein & Farr is by almost any measure the most popular law firm in Washington.

In the topsy-turvy legal marketplace for graduates of elite law schools, the best and brightest of them all are wooed by an endless succession of law firms and virtually have their pick of jobs.

Not at Onek Klein. The firm interviewed six of the 33 departing Supreme Court clerks -- a remarkable number for a place of its size. It offered to hire only two.

Onek Klein is one of a breed of small, so-called boutique firms that started to emerge about a decade ago as Washington's big firms grew even bigger, and lawyers with the luxury of choice sought an alternative to working in large bureaucracies.

For young associates particularly, the appeal of small firms like Onek Klein is in large part the opportunity to avoid the worst of big-firm legal practice: the cutthroat competition to make partner; the impersonal environment; the mega-cases in which young lawyers may spend the first few years of their career doing library research or poring over piles of documents.

"Before I got here, I didn't know working at a law firm could be so enjoyable," said partner JoAnn Macbeth, whose two years at Cravath, Swaine & Moore, the prestigious New York law firm, featured a stint as the most junior of about 14 lawyers working on a turbine generator price-fixing case.

One Supreme Court clerk, Beth Heifetz, who works for Justice Harry A. Blackmun, has accepted Onek Klein's offer. Christopher Cerf, who clerks for Justice Sandra Day O'Connor, said he is leaning toward going there. That would be a major coup in an environment in which a firm's allure is measured in part by how many clerks it has bagged in the annual Supreme Court sweepstakes, and in which even the largest law firms are lucky to snare one.

"When people go there to talk, they come back just singing their praises like no place else," said a Supreme Court clerk who has accepted a job in another city. "Everybody who's looking for a small firm in D.C. has talked to them."

"Onek, Klein & Farr is doing well this year," said Bruce Ennis of Ennis, Friedman, Bersoff & Ewing, a six-lawyer firm that competes with Onek Klein for same small pool of clerks. "It is an attractive firm to a lot of people."

Founded in 1981 by former clerks to Justices William J. Brennan Jr. (Joseph N. Onek), Lewis F. Powell Jr. (Joel I. Klein), and William H. Rehnquist (H. Bartow Farr III), Onek Klein almost instantly became the sort of firm that attracted other high court clerks. Those who did not come with the cachet of a high court clerkship had credentials nearly as stellar: law review editorships, prestigious appeals court clerkships, special assistant positions and the like.

They have built what is generally considered a "sexy" practice: Supreme Court cases, First Amendment work, health law matters, representation of states, and an array of what Klein terms "public policy litigation" -- cases with more at stake than whether one corporation triumphs over another.

Onek Klein is now on the short list of interview stops for top-credentialed law school graduates interested in working at a small D.C. firm. Others include Rogovin, Huge & Lenzner, which does a wide variety of litigation; Miller, Cassidy, Larroca & Lewin, which has a large white-collar criminal law practice; Ennis Friedman, whose practice is remarkably similiar to Onek Klein's but which bills itself as more liberal, and labor law specialists Bredhoff & Kaiser.

From year to year, as the small group of law school graduates who possess the credentials even to make it to the interview stage at such places trade gossip among themselves, all these firms are more or less hot.

This is Onek Klein's year, for a number of reasons.

In the current term alone, its lawyers argued two cases at the Supreme Court and filed briefs in nine others, offering clerks the prospect of continuing to work on cases of the caliber they handled while at the court.

Half the firm's 10 lawyers are former Supreme Court clerks, a not-insignificant consideration for current clerks considering their job options. "One thing about Supreme Court clerk-types is they like their own," Klein said.

In a town full of unhappy lawyers who work grueling schedules, Onek Klein has gained a reputation as an oasis of nice people, humane hours and interesting cases.

The firm's allure may have been heightened for applicants because they know only a few of them will get offers there. "These are people who have competed for everything all their lives and when six or seven of them are competing for one or two jobs, that gets the blood pressure up," Klein said.

And in the small, word-of-mouth world in which it operates, Onek Klein was particularly well positioned to lure clerks. Its two newest lawyers -- Jean Scott and Paul J. Van De Graaf -- had come from clerkships on the D.C. Circuit and the 2nd Circuit in New York, and they knew a number of the high court clerks between them.

"Paul and I could call our friends and say, 'We're going to be interviewing, we'd love to talk to you,' " Scott said.

This year, Klein said, "We've gotten extraordinary interest from extraordinarily talented people." But, he noted, the popularity of any particular firm can be a fleeting thing. "This time next year, who knows?" he said. "Two people could have said they're unhappy and somebody else may be hot."

For the time being, however, Onek, Klein & Farr appears to be very much the sort of law firm its founders set out to build in 1981, when Onek was leaving his post as White House deputy counsel, and Klein and Farr split off from Rogovin, Huge & Lenzner (which was itself formed five years earlier by lawyers who left Arnold & Porter).

The concept, as Onek described it, was "a place that had very interesting work, an enjoyable place, and that would always take precedence over financial considerations, so you don't end up doing things that you don't want to do or not doing things that you do want to do."

The firm does a good deal of work free or for reduced rates. "If someone comes to us and says, 'We can't afford your normal rates,' and we're interested in doing the work, we will do whatever can can that's reasonable to take it on," Farr said.

That is reflected in the bottom line, although lawyers at Onek Klein are far from the poorhouse. Most of the seven partners make in the low six figures, up from between $60,000 and $70,000 for even the three name partners during the firm's first few years, according to sources familiar with the firm's finances. Associates are paid the "going rate," in the $50,000 range for those who will start next year.

At times, interesting work also takes precedence over being on what liberal lawyers would deem the "politically correct" side of a case. Recently, for instance, Onek Klein helped the State of Arkansas write its brief and prepare for oral argument in a death penalty case before the Supreme Court.

The firm's major client is the American Psychiatric Association, for which it writes friend-of-the-court briefs on such topics as whether an insane person may be executed, and handles a prepaid legal plan under which psychiatrists can call for advice. The firm defends psychiatric malpractice cases for doctors referred by the APA.

It reviews New Republic articles for potential libel problems. Partner Peter E. Scheer serves as general counsel for former Washington Post reporter Scott Armstrong's National Security Archive, which is amassing a repository of declassified government documents about foreign policy and national security.

Onek Klein has been particularly aggressive about building up its Supreme Court practice. It regularly writes to lawyers whose cases the Supreme Court has agreed to review, offering to help in drafting briefs, preparing for oral argument, or to handle those matters itself.

Having Supreme Court clerks has helped the firm attract intresting work, and vice versa. "The number of clerks we have is an easy way to having the firm taken seriously, Farr said. " . . . Why hire a 12-lawyer firm nobody's ever heard of? Our resume helps people take a second look."

The downside, Scheer said, is "that when we do hire a lot of Supreme Court clerks, I'm afraid sometimes that other very fine people out there will think we're a bunch of snobs who only hire Supreme Court clerks, which is completely untrue." Still, he said, "Naturally, when a resume comes in that says, 'Clerking for Justice O'Connor,' you look at it."

Lawyers at Onek Klein need not suffer nightmares over whether they will make partner, because everyone who stays does. At most law firms, partners' incomes are treated like state secrets; Onek Klein's seven partners share that information with the firm's three associates because, Farr said, "it never occurred to us there was any reason for them not to know it. After all, they're all going to be partners someday."

The firm has consciously resisted growing too fast. Former partner Anne K. Bingaman left after less than a year when she thought she had landed a major asbestos case that would have required a number of paralegals and associates to staff it, and the other partners told her they weren't interested.

It remains to be seen whether the firm -- which has tripled in size since its inception -- will be able to resist the financial and organizational pressures to grow as the current group of lawyers become older and reluctant to do the lower-level tasks of younger associates. Many of its lawyers see 20 as a natural cutoff point.

"We're trying to see if we can continue to have the kind of firm that we came together to have," Onek said. "We don't want to wake up one morning and see that we're bigger than we want to be and not doing what we set out to do."