For more than two decades, the mile-long stretch of Santa Monica Boulevard in Hollywood known as Theatre Row has served as home to the city's densest plot of live theaters, drawing audiences to a diverse array of stages run by scrappy companies.

On busy nights, spectators can see works by new playwrights, revisit classic dramas or take in comedy shows. Weeknights often find the area filled with students attending acting classes and auditions.

But in the last several months, an array of challenges has mounted, and many observers believe Theatre Row's existence — and the cultural viability of the larger neighborhood — is threatened.

Rising commercial rents have already caused two of the district's most prominent companies — the Celebration Theatre and the Open Fist Theatre Company — to move. Theater leaders say others are in jeopardy.

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Some also pointed to a recent influx of marijuana dispensaries and a resurgence in criminal activity in the area, including prostitution.

"It was starting to feel a lot safer in the last five years. But in the last six months, there's been a relapse," said Olya Petrakova, who runs the theater space Schkapf with Bryan Brown. "There's more drug use in the area, and prostitution is coming back."

The problems come at a crucial time for Theatre Row, which consists of nearly 20 stages, most of which have 99 or fewer seats.

The annual Hollywood Fringe Festival, which started in 2010, brings hundreds of theater productions from around the world to the neighborhood each summer and has benefited theaters by heightening the area's public profile.

At the same time, some companies continue to recover from the effects of the recession and are struggling to make ends meet.

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"It's definitely a lot harder to sell tickets now than it was a decade ago," said Zeke Rettman, producing managing director at the Hudson Theatres. Some leaders believe that ticket prices are too expensive, and others said that it has become increasingly difficult to compete for people's attention on social media and other marketing channels.

But with the rapid gentrification of formerly marginal areas of Hollywood, bringing new construction of commercial and residential buildings and even hotels, land values are rising as well, leading to higher rent.

Open Fist's rent increase precipitated its departure. The company had been paying about $8,000 in monthly rent, but the landlord wanted to raise it by $4,000 a month.

"Commercial rents are creeping up again, and a nonprofit theater is not in the best position to compete in the market," said Martha Demson, artistic director of Open Fist.

Last year, the Celebration left its home of more than two decades on Santa Monica near La Brea Avenue because its occupancy expenses — which had started to include utilities on top of rent — more than doubled.

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In the last eight years, the cost of residing at the theater rose from $3,000 per month to roughly $7,500, according to Michael C. Kricfalusi, the company's executive director.

The Celebration, which produces gay- and lesbian-themed plays and musicals, has found a part-time space in Atwater Village; Open Fist has opted for a nomadic existence, producing plays at different venues.

The Elephant Stages, on Santa Monica near Vine Street, will likely have to vacate its home in two years because the owner plans on selling the property. With three stages as well as a resident theater company, the Elephant has seen its rents soar since it moved to Hollywood in 1999. At the time, the company paid $3,100 per month for its 99-seat Lillian Theatre alone. It now pays $6,000 for the same space.