She and her fiancé ignored that advice, but the shooting made her wonder how well the city was prepared to prevent a terrorist attack.

"It did dawn on me after my mom bugged me, but Vegas is probably a pretty easy place for a psycho to do damage," said Ms. Cunningham, a 27-year-old legal secretary. "Everybody comes and goes as they please. Who would know if that Elvis impersonator were a suicide bomber?"

Casino and law enforcement officials say the Las Vegas Strip is among the safest, most carefully monitored public gathering places in the world. But the city, known internationally as a symbol of American hedonism, has long been considered a likely prime target of terrorists. And two recent violent incidents — the New York-New York shooting and a deadly car bomb explosion at the Luxor Hotel-Casino in May — have gotten the attention not only of tourists but also of security experts.

"We have not had an event here in Las Vegas the equivalent of the events of 9/11 or anything close to that, and that hasn’t been by accident," said Bill Young, a former sheriff here and now security chief for Station Casinos, owner of 10 casinos in the area. "With all that said, it’s going to be very, very, very difficult to prevent lone criminals who have the intentions of harming themselves and others."

That was the case at New York-New York shortly after midnight on July 6. Steven F. Zegrean, 51, of Las Vegas is charged with opening fire then with a semiautomatic handgun from a balcony overlooking the casino floor. Four people were wounded, none critically, before four tourists tackled him. In the Luxor explosion, on May 7, the police have accused two men of leaving a homemade bomb in a coffee cup atop the car of a 24-year-old restaurant employee who died in the blast.

The police say Mr. Zegrean was attempting suicide, hoping that officers would kill him. The bombing, they say, was motivated by a dispute over a woman.

Las Vegas was one of four cities cited by the F.B.I. as having received specific credible threats that prompted heightened security on New Year’s Eve in 2003, and some Strip resorts were recorded on videos found in the possession of two men who earlier that year were convicted of being part of a Detroit terror cell. (The convictions were later overturned on the ground that prosecutors had withheld evidence from the defense.) In addition, several of the Sept. 11 hijackers visited Las Vegas before their attacks for what the F.B.I. believes were planning sessions.

The Strip is famous for its video surveillance of nearly every public inch of casino-resorts, scrutiny to which Mr. Young points as a deterrent "for any criminal who does not wish to be caught." In addition, more than 6,000 private security personnel supplement and train with the police force, said Kathleen Suey, deputy chief in charge of the Police Department’s homeland security division.

Still, more than 40 million tourists visit the city each year, and "there’s really no way of screening that many people without greatly limiting access," said Christopher E. McGoey, a security consultant who has advised several Las Vegas casinos.

"It’s a vacation place," Mr. McGoey said. "People don’t want to be walking around with passports or going through metal detectors or screenings. It's always going to be a relatively soft target."

In the New York-New York case, Mr. Zegrean had paced the indoor balcony for hours wearing a trench coat before the shooting. One of his tacklers, Justin Lampert, a 24-year-old Iraq war veteran from North Dakota, was surprised that it took tourists to avert a massacre.

"You would’ve thought some security guy would have seen him, since he was wearing a trench coat and it’s 115 degrees outside," Mr. Lampert said. "I would expect that to stand out in somebody's mind. They do need to spruce up security. But if they do that, they'll probably lose some of the income from people who won't come because of the hassles."

Las Vegas resorts have been leaders in adopting some new security technology, said Alan Feldman, senior vice president of MGM Mirage, owner of the Luxor, New York-New York and eight other Strip properties. While Mr. Feldman would not discuss many of MGM's security initiatives, for fear of compromising them, he did note that the company was experimenting with a facial-recognition system that could someday spot people traveling with fake IDs.

In addition, Ms. Suey noted that the homeland security division would add 28 uniformed officers this fall — the police do not disclose the division’s total strength — and that Las Vegas was one of just a dozen cities with an officer working full time at the Department of Homeland Security’s headquarters to relay information on terrorist chatter.

Both recent events were "good exercises for us," Ms. Suey said.