Set and lighting designer Michael Philippi, who worked at the Repertory Theatre of St. Louis on 15 productions, died on a sidewalk in downtown Chicago on Tuesday. He was 58 years old.

He collapsed on his way to a technical rehearsal at the Goodman Theatre, where he was working a production of "High Holidays."

The cause of his death has not yet been determined.

Although Philippi lived in Baltimore, he often worked in the Midwest. Rep audiences may remember his set and lighting designs for the 2007 Studio Theatre production of "The Clean House," a modern dwelling so elegant and airy, some theatergoers wished they could move right in.

"The Clean House" was directed by Susan Gregg, the Rep's associate artistic director. She died in July of a heart ailment. The two were frequent collaborators; they last worked together on the Rep's powerful Mainstage production of "The Miracle Worker" last season. Philippi was the lighting designer. His work at the Rep dates to 1990, when he designed the sets for "The Heidi Chronicles."

In Chicago, he frequently worked at the Goodman. His collaborations there with artistic director Robert Falls included the lighting design for an acclaimed production of "Death of a Salesman" that started at the Goodman, moved to Broadway and made a national tour that played the Fox Theatre here in 2000.

Philippi was "a gifted designer, a wonderful collaborator and a friend," said Steven Woolf, the Rep's artistic director. "Michael's artistry will be sorely missed."

Friends and colleagues are invited to share their thoughts via e-mail to condolences@goodmantheatre.org and read others' posts at goodmantheatre.org/News/condolences.aspx.

By Judith Newmark