Theatre design for both IMAX® and OMNIMAX® presentations opens up a variety of new. possibilities and presents a host of problems, some old, and many new. Many traditional concepts of theatre design, such as clear sight-lines to the bottom of the screen, are no longer justified, or even desirable. Conversely, because of the large included angles in the projection beam, projector light-ray clearances become critical at many points in the auditorium. — Audience movement and safety are important factors, and several unusual concepts are discussed. Since most IMAX® and OMNIMAX® theatres are in new construction, there are unique opportunities to optimize the audience environment, including picture, sound, and acoustics. Existing IMAX® theatres range in size from 120 to 980 seats, with 1400 seats projected. OMNIMAX® theatres range from 94 to 380, with larger theatres in the planning stage.