Kilian began as an assistant for composer Christopher Young. Mark spent almost 3 years with Chris during which period he worked on many big films as electronic score producer and composer's assistant. Some of them include Species, Copycat, Virtuosity and Hard Rain. In 1997 Mark scored his first film, Lovergirl starring Sandra Bernhard. Mark has worked as orchestrator, arranger and conductor for Paul Oakenfold, Rob D and Juno Reactor on the Matrix: Reloaded film. His special affinity for percussive music led fellow composer Christophe Beck to hire him to record and produce the electronically manipulated percussion element of the score for Elektra.
In 2004 Mark went to South Africa to score Tsotsi for writer-director Gavin Hood along with South African composer Paul Hepker. The film won the 2005 Academy Award for best foreign film. Mark and Paul went on to score Gavinís next film Rendition, traveling to Morocco and South Africa to research and record the music. They also scored The Bird Canít Fly, a Dutch-South African co-production.
In 2007 Mark traveled to India to record the music for Santosh Sivanís Before the Rains. He also wrote the music for Michael Skolnikís award winning documentary Without the King which was recorded in South Africa. Mark just has scored Traitor, a thriller starring Don Cheadle and Guy Pierce.