HAVANA -- Moments before the entourage of black Mercedes-Benzes rolled into the University of Havana and the swarm of large men with earpieces and dark glasses trooped through campus, someone ran into Cat Linenberger's classroom shouting, ``Fidel! Fidel!''

The 20-year-old foreign exchange student from St. Petersburg wasn't sure what was happening. It was her second day in Cuba.

Then a burst of applause rang out and she saw a bearded old man in an olive-green uniform emerge from one of the cars. She recognized him instantly -- President Fidel Castro.

``I was so close I could have dropped my textbook on his head,'' said Linenberger, who confessed to joining in the adulation for the Cuban leader.

``People were going nuts for him. I couldn't believe it. This definitely wasn't in our syllabus.''

Linenberger is one of more than 100 U.S. students studying this year with American universities licensed by the U.S. Treasury Department to offer classes in Cuba. She came to Havana with a study program sponsored by Tulane University.

A few years ago, the Latin American studies major, who is writing her thesis on Castro, probably would have had to settle for consulting books and interviewing sources over the phone to complete her research. The 36-year-old U.S. embargo prohibits Americans from traveling to Cuba without a license.

Similar programs

But, since the law was amended in 1995 to allow for foreign exchange programs, more than a dozen American universities have arranged programs in Cuba, according to Beth Weaver, a spokeswoman of the Treasury Department's Office of Foreign Assets Control. So far, no Cuban students study at U.S. universities.

This summer at least a half-dozen universities held classes in Havana, including the State University of New York at Buffalo, Wake Forest and St. Mary's University in San Antonio.

Other U.S. schools with programs in Cuba include Harvard, Johns Hopkins and Hampshire College of Amherst, Mass.

Diane Steffan, 25, a graduate student in bilingual education at Buffalo, said her Cuban-born mother was strongly opposed to having her daughter spending dollars in a country she had been forced to leave more than 30 years ago.

``She was like, `No way,' '' Steffan said. ``Then she eased up. And eventually she got excited for me to bring back memories.''

`The spy'

Enduring tensions have made studying in Cuba different from other countries.

Buffalo students are often accompanied around the capital and joined in class by a man from the Interior Ministry who calls himself Doug. They call him ``the spy.'' The chummy official keeps tabs on what students ask and what the professor says.

``It's just a way for them to keep an eye on us,'' said Jose Buscaglia, a Buffalo professor teaching classes on architecture and history to 33 students. ``I guess they think some of the students might be working for the CIA.''

Firsthand experiences are not all positive. Mike Milch, 20, a politics major at New York University, learned about the surge in petty crime since the Cuban economy nose-dived in the early 1990s after the fall of the Soviet Union. The 10-speed bicycle he brought from home was stolen on his second day in Havana. He brushed it off as the drastic measures impoverished people are driven to. What he couldn't dismiss was all the hustling.

``Everywhere you go, someone's trying to sell you something,'' Milch said. ``They treat you like you're a walking dollar. It's hard not to feel resentment.''

Cash needs

The desire for cash is one of the main reasons Cuba has been eager to accept American students and why the United States has been reluctant to let them go, said Jerry Poyo, a history professor in Havana with 16 students from St. Mary's University. The travel licenses granted by the Treasury Department bar students and professors from spending more than $100 a day in Cuba.

Yet St. Mary's students still had time to browse for trinkets in a government-sponsored tourist zone during their packed two weeks on the island, which included touring an AIDS sanatorium, meeting members of the National Assembly and debating freedom of the press with Cuban journalists.

``This is not about spending or not spending money,'' said Poyo, while a few of his students haggled with one of many vendors on Old Havana's recently restored Plaza de Armas. ``It's about interaction, learning and getting beyond the conflict people always read about.''

Sipping bottled water on the stoop of one of the University of Havana's many dilapidated buildings, Nicolle Ugarriza, 26, of Miami Beach, thought about what she might have done if she had met Castro. The first-generation Cuban American said she wasn't sure how she would react. Her family wouldn't be thrilled, she said.

``At home everyone has a programmed reaction,'' Ugarriza said. ``But underneath that there is a tremendous curiosity. I've heard about Cuba forever. So it was time for me to experience it myself.''