CHICAGO (AP) _ Twenty minutes into the performance of ``The Best Man'' at a Chicago theater, veteran stage actor Gene Janson, onstage with fellow performer David Darlow, unexpectedly put his head in his hands.

When Darlow asked Janson if he was OK, ``He replied that he was not,'' said James Bohnen, artistic director of the Remy Bumppo Theatre Company, which is producing the play.

Darlow rushed off the stage to get help, and a nurse in the matinee audience came to Janson's aid. Janson, 72, was taken Wednesday to Lincoln Park Hospital, where he died shortly after of a heart attack, said his son, Christopher Janson.

``There is a certain poetic irony to his death,'' Christopher Janson said. ``He died doing what he loved, which was being on the stage and in a play he was so proud of.''

In the Gore Vidal drama, Janson portrayed a fictional former U.S. president who dies unexpectedly. Bohnen said the role was one of Janson's finest in a 50-year career.

``He brought so much to his character,'' Bohnen said. ``He was having the time of his life with this part.''

Janson worked mainly on the stage, although his film credits included ``The Blues Brothers,'' ``While You Were Sleeping,'' and ``My Best Friend's Wedding.'' He also appeared in TV shows and commercials.

Janson was familiar to Chicagoans as a pledge drive spokesman for public station WTTW-TV, a job he held for more than 20 years.

Remy Bumppo planned to resume ``The Best Man'' with an understudy in Janson's role, a spokesman said Friday. The company has dedicated the rest of the play's run at Chicago's Victory Gardens Greenhouse Theater to his memory.

Besides his son, Janson is survived by a wife, two daughters and four grandchildren.