Jeff Conaway, the personable actor who won television fame on the sitcom “Taxi” and movie success in the musical “Grease” three decades ago and who later publicly struggled with drug and alcohol abuse, died on Friday in Los Angeles. He was 60.

He died of complications of pneumonia at Encino Tarzana Medical Center after being taken off life support on Thursday, a talent representative, Phil Brock, said.

Mr. Conaway was found unconscious at his home in the Encino section of the city on May 11 and was kept in a coma medically without ever regaining consciousness, Mr. Brock said. He said Mr. Conaway had been struggling with back problems and treating himself with painkillers while in weakened health.

Mr. Conaway’s addictions to alcohol and drugs were well known because of his appearances in 2008 on the reality series “Celebrity Rehab With Dr. Drew,” starring Drew Pinsky. Mr. Conaway often appeared high and belligerent on the show. He had agreed to participate against the wishes of his agents, Mr. Brock said.

Mr. Conaway said numerous back surgeries were responsible for his addiction to painkillers. In early 2010 he had a serious fall that left him with a brain hemorrhage, a broken hip and a fractured neck.

Mr. Conaway spoke openly of his problems in 2008 when he appeared on Howard Stern’s radio show and told the host, “I’ve tried to commit suicide 21 times.” Asked about his methods, he replied, “Mostly it’s been with pills.”

In late February and early March, Mr. Conaway and his girlfriend of seven years, Victoria Spinoza, a singer who records as Vikki Lizzi, filed temporary restraining orders against each other, trading accusations of theft and physical violence.

Mr. Conaway had continued to work in films and television in recent years, but his career had plummeted since his greatest popularity, in the late 1970s and early ’80s.

The film version of “Grease,” starring a rebellious John Travolta (as Danny Zuko) and a wholesome Olivia Newton-John (Sandy) as improbable 1950s high school sweethearts, opened in June 1978, with Mr. Conaway in the supporting role of Kenickie, Mr. Travolta’s bad-boy sidekick. The tough-talking but vulnerable Kenickie goes through his own trauma, believing that his girlfriend, Rydell High’s bad girl Rizzo (Stockard Channing), may be pregnant.

Three months later, “Taxi,” a sitcom about a group of New York cabdrivers, had its premiere on ABC. The show’s ensemble cast included Judd Hirsch, Danny DeVito, Andy Kaufman, Tony Danza, Christopher Lloyd and Marilu Henner. Mr. Conaway’s character, Bobby Wheeler, was a vain and handsome aspiring actor who never seemed to get a break in his show business career.

In an admiring review of the show in 1979, John J. O’Connor, writing in The New York Times, described a scene in which Bobby had accidentally let his friend Tony’s two pet fish die. “I guess it was just their time,” Bobby tells Tony desperately, adding that maybe the deaths were “one of those murder-suicide things.”

The series lasted five seasons, but Mr. Conaway left after the fourth. In 1989, he explained his reason for the departure to The Toronto Star: “In ‘Taxi,’ I kept doing the same scene for three years. I was underused.”

Jeffrey Charles William Michael Conaway was born on Oct. 5, 1950, in New York City. His parents, a struggling actress and an advertising man, divorced when he was a boy, and he divided his time between his mother’s apartment in Flushing, Queens, and his maternal grandparents’ home in South Carolina.

He began acting as a child and made his Broadway debut when he was 10 in a small part in “All the Way Home,” a well-received adaptation of James Agee’s novel “A Death in the Family,” starring Colleen Dewhurst, Arthur Hill and Lillian Gish.

Growing up, he modeled, appeared in commercials and played in a rock band. He spent a year at the North Carolina School of the Arts, then transferred to New York University. But because of a job offer, he never graduated.

That job was in the original Broadway production of “Grease,” which opened in 1972. He understudied several roles but was never cast as Kenickie, the role that made him famous in the film version. Instead, he eventually took over the role of Danny, the romantic lead.

A few years after “Taxi,” Mr. Conaway returned to Broadway in a new musical, “The News,” in which he played the editor of a big-city tabloid. But the reviews were negative, and the show closed after three nights. He continued to appear in films and did television again, most successfully in the 1990s science fiction series “Babylon 5.”

His last film work was as the voice-over narrator in two fantasy dramas, “Dante’s Inferno Documented” and “Dante’s Purgatorio Documented,” both in postproduction. His final screen appearance was in the film “Dark Games,” a thriller scheduled to be released this summer.

Mr. Conaway married and divorced three times. After an early marriage that lasted less than a year, he married Rona Newton-John, the sister of his “Grease” co-star, in 1980. They divorced in 1985. His third wife was Keri Young, from 1990 until their divorce in the early 2000s.

His survivors include two sisters, Michelle and Carla, and a stepson, Emerson Newton-John, a racecar driver.

When Mickey Rourke, after fighting his own battles with addiction, earned an Oscar nomination for his performance in “The Wrestler” two years ago, an interviewer asked Mr. Conaway what he thought about Mr. Rourke’s comeback.

“Hollywood can be a very stinging town,” Mr. Conaway said on a video posted byHollywood.TV on YouTube. “They say it’s a forgiving business. It’s not that forgiving.”

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