Original executive producers John Wells and Michael Crichton reprised their roles. Lydia Woodward also returned as an executive producer and writer. Carol Flint became a fourth executive producer. Flint was replaced as co-executive producer by Christopher Chulack. Chulack was previously a regular director and a producer for the third season. Paul Manning left his supervising producer role but remained involved with the series as an executive consultant. Long-time crew members Lance Gentile and Neal Baer were promoted to producers for the fourth season. Third season co-producers Wendy Spence Rosato and Penny Adams returned to their positions. Jack Orman and David Mills joined them as new co-producers and writers. Mills left the show midway through the season. Following his departure Adams was promoted to producer and Richard Thorpe and Michael Salamunovich joined the production team as co-producers. Thorpe had previously worked on the series as both a cinematographer and director. Salamunovich was the series unit production manager for the first three seasons and continued to fulfill this role as a co-producer. Michael Hissrich continued to serve as an associate producer. Manning, Hissrich, and Gentile all left the crew with the close of the season.