This report first reviews the history of model testing as an aid to the designing of auditoriums, beginning in 1913 with Sabine's spark photography [W. C. Sabine, “Theater Acoustics,” Amer. Architect. 104, 257 (1913)] and eventuating with the more sophisticated Spandock three‐dimensional models [F. Spandock, “Akustiche Modellversuche,” Am. Physik 20, 345–60 (1934)] scaled down to 1:10 and 1:5, including models with improvements by Japan's NHK Laboratories. It also reviews the two‐dimensional optical model tests we use at UCLA [as developed by R. W. Leonard “Simplified Optical Modeling for Auditoriums,” J. Acoust. Soc. Amer. 26, 937 (A) (1954)], which are expedient for determining approximately optimal shapes in plan and sections, followed, when deemed necessary, by tests of three‐dimensional models (optical and acoustical) that range in scale from 1:1 to 1:4, for critical (often repeated) segments of walls and ceiling, and down to 1:24, for the walls, floor, and ceiling, which can be examined separately and as progressively assembled into the complete model of the auditorium. Examples are presented of procedures and findings in connection with the acoustical designing of several multipurpose auditoriums and a theater in the round (220°) with thrust stage. Acoustical model testing reveals diffraction effects and echoes (or their absence) and helps in the designing of auditoriums that optimize early reflections, diffusion, reverberation, and sound‐level distribution.