In 1969, after representing the U.S. Girl Scouts for three months in a program to promote scouting in Pakistan, Dorcas R. Hardy, then 23, climbed Africa's Mt. Kilimanjaro during a trip around the world.

Hard as it was, that trek up the mountain was nothing compared with the task she now faces. Hardy, 40, is the new commissioner of Social Security.

She heads an agency that has 76,000 employes and will send $206 billion in benefits next year to 37 million Social Security recipients, plus $10.5 billion in Supplemental Security Income payments to 4 million poor aged, blind and disabled people. Making sure "the checks arrive on time" is one of the hardest jobs in government.

Hardy, assistant secretary of Health and Human Services for human development services from 1981 to 1986, is a conservative Reagan loyalist with a reputation as a tough -- some say harsh -- administrator.

Part of that reputation derives from the fact that as assistant secretary in charge of programs for some of the nation's neediest people -- children without families, children in the Head Start preschool program, the aged -- she sometimes proposed funding cuts. She has also been accused (falsely, she said) of bending the rules in some grant awards.

But her personality is a factor, too. In conflicts, she tends toward a confrontational style, and she knows it. She concedes that she has "a combative nature . . . . If I'm concerned about something I'll fight and keep fighting."

She is impressed but not intimidated by her new job. "I'm beginning to realize it's one of the toughest jobs in government. Sometimes the press calls government unmanageable, but if you figure out what you want to get done, tell your troops what you want of them, you can get it done," she said in a recent interview.

Her firm managerial style is evident in her decision, as one of her first priorities in her new job, to "look at the corps of senior managers to see if we've got the right people . . . . Yes, I'm a tough administator. I believe staff should be accountable."

She said people sometimes get stale in jobs, and she has told managers who are in the Senior Executive Service -- a Civil Service corps of super-administrators -- that "if they've been in the job more than three years, they should bring me a list of places they'd like to work" other than their present slots.

That directive startled some of Social Security's 60 SES members, but Hardy said she does not intend to purge employes -- simply to shift some around. Overall, she said, "we have a good, long-time labor force."

What is it that she wants to get done? "I have five umbrella goals. The first is protecting the integrity of the trust funds. There is no problem now, but we must keep a close eye on the financing, we have to keep looking at the reserves for the future.

"There is technology. Make sure we get into the 21st century soon, but not technology for technology's sake, not putting in PCs personal computers for extra glitz and glitter." Next year, $300 million will be spent on the ongoing program to modernize the once woefully archaic computer system.

A third goal is improving service to beneficiaries through the 1,340 Social Security field offices. Hardy does not plan major shutdowns of field offices, despite rumors last year that the Social Security Administration was moving to close a third of them. "Every year about 11 or 12 close down" or are shifted from one area to another, and "I don't expect more than that" this year.

Fourth: "A major issue is public confidence in the system. I talked to an 18-year-old girl and she said, 'It's not going to be there when I get there.' We do expect it to be there. People will get the benefits, and we have to get them to understand that."

Finally, there is the budget requirement to "downsize the labor force. We must cut 14,000 more by 1990" under a long-term plan to cut full-time equivalent jobs from about 80,000 in 1985 to 62,900 by the end of the decade. "It will all be done by attrition," she said, not by firings.

Hardy has more immediate problems, too. One will be rapid issuance of 9 million to 13 million new Social Security cards for children under 18, presumably before the end of the year, if Congress retains in the tax bill a requirement that parents must give Social Security numbers for all children over five when claiming them as income tax deductions.

Because Hardy worked for Ronald Reagan when he was governor, many people think she is a native Californian, but she was born in Newark, N.J., and grew up in surrounding suburban areas.

Her father, C. Colburn Hardy, was a middle-of-the road Republican who served in the New Jersey assembly for two terms before World War II and was close to the late liberal Republican senator Clifford P. Case (N.J). Today her parents live in Florida, where her father is "a writer on financial investments." Her mother is public relations director at St. Mary's Hospital in West Palm Beach. "I'm more conservative than my parents," Hardy said.

Her first political job was as a summer intern in Case's office in 1967, when she was 21, a year away from receiving her BA in government from Connecticut College.

After climbing Kilimanjaro, she worked again for Case; at that time, she said, she was "not a campaign junkie, but I guess I became one later." Next, through GOP contacts, she became a special assistant to Steve Hess, director of the White House conference on children and youth in 1970-71.

From there she moved to the U.S. government's Cost-of-Living Council as executive director of the Health Services Industry Committee from 1971-73.

Then came Reagan. "Dr. Earl Brian, who was on the Health Committee, was in the Reagan Cabinet in California . He offered me a job in California." From 1973 to April 1974 she was assistant secretary for health there, and she went on to campaign for Reagan when he challenged President Gerald R. Ford for the GOP nomination in 1976. In the same year she got an MBA from Pepperdine University. But her full-time work from 1974 until Reagan captured the presidency in 1980 was at the University of Southern California medical school, where she was an associate director at the Center for Health Services Research.

Another associate director was David Winston, a health specialist who later worked for then-Sen. Richard Schweiker (R-Pa.) on Capitol Hill and who strongly pushed Hardy for a federal job when Reagan took office and named Schweiker HHS secretary. She joined the administration as HHS assistant secretary.

In her five years as assistant secretary for human development services, Hardy has been criticized -- and scrutinized -- several times for allegedly ignoring the rules governing grant awards. In 1984 the General Accounting Office criticized her for creating "the appearance of lack of impartiality" by her presence at meetings in which her agency awarded $493,000 in grants to her former unit at USC. However, the GAO said she did nothing improper to influence the award, and she has maintained that she did not take a position on who should get it.

More recently she has been criticized by Rep. Ted Weiss (D-N.Y.) on grounds that too many grants for child-abuse projects were made out of turn, without reference to the agency's complicated system of evaluating grant applications. In hearings of Weiss' intergovernmental relations subcommittee, Hardy and Weiss clashed repeatedly, with Hardy strongly denying suggestions that grants had been deliberately channeled according to the conservatism of competitors. Hardy insists that her aim was to break up bureaucratic "fiefdoms and baronies" in the award of grants and to make sure some of the money went to people other than "Beltway bandits."

She defends herself also against the charge that she deeply slashed programs for the most defenseless members of society. Many of her proposals, she said, simply involved keeping programs from increasing, not cutting them. But she is not defensive about the cuts she did recommend. Her philosophy is that extra money can sometimes harm a program.

Sometimes, she said, "more is less." She added that in many cases, "U.S. funds should not be used as the first dollar -- or the only dollar -- to cure problems."