The agenda for the first session of the year of the Senate Judiciary Committee yesterday sounded painfully boring: "organizational meeting," the official Senate schedule announced.

But the big meeting room in the Dirksen Building -- almost never used for any Judiciary Committee gathering in the past -- was filled with people. Latecomers had to stand.The press seats were filled.

The chairman of the committee bantered with members and staff. He posed for picture. Tourists by the dozen trooped in to catch a glimpse of him and take his picture.

This was the first public meeting of Ted Kennedy's Judiciary Committee, and that set it apart from any similar session in memory. At the age of 46 -- long before his time by traditional Senate standards -- Edward M. Kennedy (D-Mass.) has assumed the chairmanship of a major Senate committee, and he intends to make the most of it. The public, the news media and his Senate colleagues accept this fact with emotions ranging from enthusiasm to fatalism, but all of them are playing along.

So already Kennedy's every move as chairman has been the subject of scrutiny and comment. He has been accused of trying to "take over" the committee, of trying to diminish the influence of other members, of building a new empire.

Kennedy himself grins when asked if he is becoming a dictatorial committee chairman. "We want to make it more efficient," he said in a recent interview. "We have a full agenda."

In fact Kennedy has an extraordinarily full agenda. The bills he talks about bringing out of Judiciary could easily consume most of the Senate's legislative time this year -- which is an important reason why many of them probably will not emerge from the committee during 1979.

Kennedy says he would like to act on legislation to deregulate the trucking industry, rewrite the federal criminal code, provide a new charter for the FBI, revamp the Law Enforcement Assistance Administration, revise antitrust laws, give consumers the right to sue in antitrust cases, set new standards for permissible mergers and takeovers, revise immigration and refugee laws, reform the federal courts, and more. Kennedy also plans to hold the Carter administration to its pledges to appoint 152 new federal judges according to merit, emphasizing the appointment of women and minorities.

Whether Kennedy can get much of this through the Congress is an open question, but there is no doubt that the intensity of activity suggested by that list will guarantee continued and extensive public exposure for the senior senator from Massachusetts. More than a few of his colleagues assume that is what Kennedy wants most in this uncertain political season, when he apparently wants to be always ready to make a run for the presidency without ever declaring his intentions or appearing too eager.

Which is not to say Kennedy has no interest in the substance of these issues. He and his squadrons of young, bright and energetic associates all seem to feel that the issues before Judiciary can provide a vehicle for an assertion of liberalism that doesn't cost money -- perhaps the only kind of liberalism Congress will tolerate this year.

(Kennedy will be pressing for another sort of cost-free activism on the health subcommittee of the Human Resources Committee, where he will continue to push a hospital cost containment bill.)

Kennedy's staff scoffs at reports that he is trying to seize undue power as chairman of Judiciary, noting that he already has won the most important battle -- a working majority that can be expected to support him most of the time. The old Judiciary Committee under James O. Eastland (D-Miss.) was closely balanced, and the liberal Democrats never could be confident of carring the full committee.

But Kennedy and his allies persuaded the Senate's Democratic Steering Committee to put three Democrats sympathetic to the new chairman on the panel. They are Max Baucus (D-Mont.). Howell Heflin (D-Ala.) and Patrick J. Leahy (D-Vt.). With the departure of three Southern conservative Democrats who served on Judiciary in the last Congress, there now is a clear liberal majority on most issues, according to committee sources.

To get those three to serve on the committee, Kennedy had to abandon his earlier plan to abolish all but four of judiciary's 10 subcommittees. Both Baucus and Heflin will be given small subcommittees -- as yet unnamed -- and corresponding staff allocations. Leahy will be given a share -- up to about $200,000 -- of full committee staff funds to hire people of his choosing. The Vermont Democrat did not want his own subcommittee.

Kennedy's efforts to assuage the new members have been duplicated in his treatment of the veterans. He has gone out of his way to by sympathetic to fellow Democrats, and has taken a conciliatory pose with the Republican minority as well.

However, Kennedy had hopes for changing committee procedures in ways that the Republicans don't all like. Yesterday Kennedy began to dicuss the imposition of formal rules, something the committee has avoided in the past. The most important ones would allow senators to cast votes by proxy when they cannot attend a committee meeting -- which was impossible when Eastland was chairman -- and would allow a majority to vote to cut off committee debate on any subject.

At the organization meeting yesterday Kennedy chose not to try to push these through, but instead appointed himself and Sen. Strom Thurmond (S.C.), the ranking Republican, as a committee of two to work out a compromise. Committee sources on both sides predicted an amicable resolution of the rules issue yesterday.

The Carter administration, however, has not been so reassured by the new chairman of Judiciary. Some of its officials are fearful of the prospects for repeated public clashes with the charismatic and eloquent Kennedy, so often touted as a potential rival to Jimmy Carter.

"Kennedy is going to make that committee a forum for practically any issue he can seize upon," one senior administration official predicted. "I'm fearful that Senator Kennedy will emphasize the points on which we don't agree. And of course, his staff will be goading him to be very activist and to take on the president."

With the new positions available to him as chairman, Kennedy has been able to add several dozen new staff members to his personal retinue.

According to an informed source, the administration may get an early example of its fears today, when Kennedy announces his version of the Law Enforcement Assistance Administration legislation, proposing a budget for LEAA substantially higher than appears in Carter's new budget.