Ken and Charlotte Hennigan left their high-ceilinged, marble-floored home in Tehran 38 days ago. They left their car in the carport, and their Christmas cards unaddressed. They left their electric organ and most of Ken's clothes, but took their daughter Janet, 17, and the family poodle, and 125 pounds of luggage each, and got on a chartered flight with 219 other Westinghouse employes and their families.

Less than 24 hours later they were on a bus from Dulles Airport to Cockeysville, Md., where Westinghouse had a hospitality suite waiting in the Hunt Valley Motel and rooms reserved and ready.

The day they left, Dec. 8, the headquarters of the Grumman Corp. in Isfahan, about 300 miles from Tehran, was burned down by antigovernment demonstrators. Firebombs had been thrown at the homes of an American, and a British diplomat, and 600 American government families had been ordered to leave the next day.

Were they scared?

"No," said Charlotte. No one cried on the trip back, she said, not even the kids. "It was one big happy family."

Other Americans have been leaving Iran in droves, thousands in the last month as violence increased and strikes made living more difficult. On Dec. 23, an American businessman in Ahwaz was killed, and the next day the U.S. Marine guards at the American Embassy fired tear gas at demonstrators who set a car on fire outside the embassy compound.

The Hennigans are part of a growing world of international technocrats, expatriots transplanted from places like Fort Worth (Bell Helicopter), Long Island (Grumman Corp.), Minneapolis (Control Data Corp.) and Delaware (Dupont). In Iran, 500 American firms ahd offices and investments of about $700 million and other countries also have sizable business colonies there, selling everything from jets and computers to expertise. By the time the Hennigans were evacuated, there were about 45,000 Americans in Iran, ebough for a city the size of Cheyenne, Wyo. There was also Kentucky Fried Chicken in Tehra, discos downtown, and a juniorsenior prom in one of the major hotels every spring.

"We'd hoped to go back," Charlotte said. "Janet's a senior and she really wanted to graduate with her class. But now we hear they've closed the T.A.S. (Tehran American School) for the rest of the Year." So now the Hennigans are living in a Best Western Motel near Westinghuse's suburban Baltimore plant, looking for an apartment or a house, and hoping Ken can get back and get the rest of his clothes. Their older daughter, Lori, 18, had left Iran to start college in Missouri last fall.

The Hennigans' experiences in Iran are typical for many Americans stationed there. Americans react to living in foreign countries in different ways; there are those who reproduce American ways of life and immerse themselves in an American community, and those who become involved with the local culture in varying degrees.

From September on, violence in Iran escalated, as did hostilities toward Americans and other foreigners. But, while the news reports were filled with riots, killings, strikes, the burning of movie theaters and banks, window smashings and pro- and antishah marches, life for the Hennigans -- and for many Americans -- was basically unaffected by the country's traumas.

"It wasn't so much fear as invonvenience," said Charlotte Hennigan. "Like under the curfew, school events started earlier. We went to a play at 5 that ordinarily would have been at 7, and the sports banquet started at 3:30. And the clubs on the base closed early so the Iranian workers could get home on time."

Ken Hennigan grew up on a farm in Oklahoma, and his wife in Durango, Colo. They's lived in Glen Burnie, a subdivision in a suburb of Baltimore, for 10 years before deciding to go to Iran.

"We had several objectives in going," Ken said as he sat on the turquoise plastic chair in their motel room. "Travel, adventure, an opportunity to see how other people live. And, of course it was a good job opportunity for me too." He was Westinghouse's manager of "ground radar programs," part of a defense project that included training Iranians to use the equipment.

"We discussed it for several months," said Charlotte, "and we all wanted to go.Especially when we found we could take our dog... I was worried about the language, and the mail. I didn't know if I'd get any letters. And I was worried there wouldn't be an orthodontist, because both the girls had braces. As it turned out, there was a great orthodontist." Charlotte got a job there as an accountant with the U.S. Army.

They lived in a three-bedroom house in the northern section of Tehran, where most of the foreigners live. All houses and offices have walls around them, they said, and most of the houses have swimming pools. A driver picked Ken up at 7:30 every morning, and the girls walked to a bus stoop, to catch the bus to school.

"We didn't have any culture shock," said Janet, a slim blond with neatly curled hair.

Martial law was imposed in Iran on Sept. 8, after nine months of sporadic rioting in cities around the country. The day martial law was imposed, Iranian army troops had fired into a crowd of demonstrators, killing more than 50 people. Teen-agers had led what correspondents described as an "angry rampage" for two hours, and stores and gas stations had been set on fire.

Martial law meant a curfew between 9 p.m. and 5 a.m., and violators would be shot at after one warning. It meant press censorship and no more than two people could meet together -- you had to get a permit to have a party.

"We had a great birthday party for Janet," said Charlotte. "About 30 kids came and they had a great time."

Both girls were cheerleaders at the T.A.S., which had three football teams so that they could play each other. The colors of the varsity team were red, white and blue. The T.A.S. was only for children with American passports, but was not the only school for foreigners there.

Overall, the Hennigans have fond memories of their years in Iran. They had new experiences and met people from many other countries.

"We learned to square dance," Charlotte said, "and Ken learned to play tennis. There was so much to do." She played with the American Wives Club bowling team.

Ken said that "it was exciting for me just to learn to get around in the world. Why, I could send Janet on a trip to Russia and she'd know what to do... One thing that illustrates it for me is that now I'm used to standing in line with all sorts of people. In front of me is someone speaking German, and behind me someone Japanese. It would seem dull to me now to always be in lines with just Americans. Not that we don't love our country, because we do."

Janet agreed that the "opportunity to travel" was the best part of living overseas for her. "I got to go to Turkey last year for a basketball competion; we played the American school in Ankara. I think it was neat to compare the way the Americans lived in Turkey to the way we lived... for one thing they had a much better bus system. But they did about the same things we did on weekends -- parties, going to a disco, softball games. But there they all lived on the base, it was like a little America there..."

None of the Hennigans had a chance to learn much of the local language, Persian. "You don't really need it," said Charlotte. "I know lots of words, but not sentences. My maid spoke excellent English. I think they teach it in the schools there, and everyone is always wanting to practice their English on you. It's a deterrent to learning Farsi. People will even call you at random just to speak English on the telephone."

The Hennigans felt hampered by government-imposed protocol and had few social contacts with Iranians. They chose the Tehran American School because it was less of a change for their two daughters.Since charlotte worked for the Army, they had commissary and A.P.O. privileges, which allowed them to avoid the time-consuming shopping in Iranian stores that could mean, as another American business wife described it, three hours just to get money out of a checking account.

The Hennigans knew only one American woman who traveled to villages outside of the capital city, working with a birth control program. "The stories she'd tell," said Charlotte, raising her eyebrows slightly.

Americans who lived until recently in Iran are particularly puzzled at the change in attitudes toward them."Until this turmoil Iranians cared a lot for Americans," Ken said. "We felt like they loved us."

Charlotte recalled an incident where an American child was lost on a Boy Scout mountain-climbing expedition. "The whole town up there went out to look for him; people would even stop you on the street to ask if you'd heard anything about him, or if the family was all right. I always felt it was very sincere... I don't know who's changed their minds."

But none of them experienced any hostility. Their lives were afected little by the turmoil, other than the shortage of cooking gas, the occasional electricity outages, the curfews.

As Ken said, "The American community in Iran was a lot like living in Glen Burnie."