The Second City Training Center isn’t just doing it for laughs.

For nearly 25 years the Chicago-based company has turned teaching improv into a business, growing from a few workshops to three centers in Chicago, Toronto and Los Angeles.

Since it began in 1985, The Second City Inc.’s training center has molded aspiring actors and comedians in the improv tradition that has propelled many of its alumni to stardom. However, the instructional arm of the venerable comedy theater has been working to broaden its reach, making itself not just a place for aspiring Stephen Colberts and Tina Feys, but a place for novices as well.

The result is that by embracing a new strategy, the training center has sparked dramatic growth despite nearly 20-plus years since its founding. With a wider slate of classes and improved marketing efforts, the center’s student enrollment increased 25 percent between January 2008 and January of this year, according to Second City Training Center President Kerry Sheehan.

Although the center’s approach is new, the core of its strategy is anything but. The company continues to embrace the tradition of the Second City theater, using it to attract both career-minded and casual improv students.

“Most of the people that come here cite the reputation of the company as what led them to us,” Sheehan recently said. “It’s huge, it’s absolutely huge.”

Second City began in 1959 when the theater opened in Chicago’s Old Town neighborhood, staging plays and improvisational theater for 16 years before a television show in New York boosted the comedy shop’s profile nationally.

NBC premiered “Saturday Night Live” in 1975 and theater alums John Belushi, Gilda Radner, Dan Akroyd and Bill Murray became key members of the early casts, helping elevate the sketch-comedy show into the pop culture pantheon. After those four left an indelible mark on SNL, the late-night sketch show has looked to Second City’s stages to find more cast members.

“In both Chicago and Toronto, SNL sparked poaching from Second City,” said Mike Thomas, author of the forthcoming book “The Second City Unscripted.”

In researching his book, Thomas found that respect for the comedy shop extended beyond its relationship to SNL. He interviewed alumni and outsiders of Second City, with the likes of Colbert, Alan Arkin and Conan O’Brien offering their praise.

“Second City is extremely well-regarded in the comedy world,” Thomas said. “A majority of people I spoke with for the book gave Second City a ton of credit for getting them where they are today.”

The industry’s reverence for The Second City has filtered down to prospective students for the training center. Twenty-year-old aspiring actress Callie Bolster from Indiana was well aware of the company’s reputation when she made her decision to start taking improv classes in the fall.

“Everybody pretty much started out here and that definitely helped,” she said.

Bolster is currently enrolled in the center’s improv program where, like with many Second City courses, she pays $275 for an eight-week course that meets once a week for three hours.

In addition to improv, the center has classes devoted to writing, acting, music and youth programs. The center’s cornerstone program is the conservatory, an advanced study of improvisational acting that requires taking six $275 classes to graduate.

Enrollment in programs across the three training centers increased to 2,700 students in January from around 2,200 in January 2008. At its largest center, Chicago, enrollment has risen 10.8 percent over the same time period, with the writing program posting an 18.6 percent jump to 325 students from 274.

The most significant jump in the number of students for a program at the Chicago center has been the improv classes, which increased 11.7 percent to 638 students in January from 571 in January 2008. The improv classes at are divided into five levels, ‘A’ through ‘E’, with the A-level classes open to beginners and not requiring an audition.

The introductory classes are increasing in enrollment because the number of people wanting to take improv classes just for fun has risen, Sheehan said. The center aims to bring in more beginners and encourage repeat customers by offering a breadth of classes. Such was the case with current 25-year-old improv student Isaac Kricheli from Chicago.

“The beginner classes are more like a hobby thing,” he said. “For me it started as a hobby, but I liked it enough to where I wanted to continue doing it.”

Kricheli, who has been taking classes at Second City off and on for more than two years, said the center has offered him an entertaining escape, which has kept him coming back. Now he’s an advanced student taking conservatory classes.

Although Kricheli has become more serious about studying improv, Sheehan said about 50 percent of the company’s students maintain merely a casual interest in learning the craft.

The center’s strategy to attract casual students is a departure from the approach employed by Annoyance Productions Inc., a Chicago-based improv theater, which also offers classes to the public.

“In our program there are a higher percentage of people who are doing it as a career or a way to enhance their career,” said Jennifer Estlin, president of Annoyance.

Annoyance’s casual students account for only about 10 percent of enrollment, and the theater does not have plans to market to casual students in the near term, Estlin said.

Conversely, Second City’s center has sought to increase its marketing to casual students since Sheehan became president in fall 2007, finding success with creating a printed edition of the course catalog for the first time.

“We track why people come here, and we have seen that people are hearing about us through the print piece,” Sheehan said.

With enrollment rising during the last year, the center is expanding its Chicago location, adding 50 percent more space to accommodate an expanding slate of programs, including more advanced classes, as well as youth programs.

The additional space, which is scheduled to be completed by the end of June, is the only planned expansion for the center in the offing. However, the company is experimenting with workshops and weeklong immersions in cities where it doesn’t currently have centers.

For now Second City will focus on increasing business in its existing locations by appealing to a broader audience, letting them know they’re just as welcome at the center as experts in improv.

“Second City might be a little intimidating, but we want people to come and join our community,” Sheehan said. “We aren’t some elite, weird group that only let people in of a certain category.”